As an Exercise Scientist I get a bunch of emails on this topic so I thought I'd save myself some letter-writing time and discuss publicly how we can best maintain our focus and commitment to our exercise program, as it seems to be a challenge for many of us.
We all talk about regular, consistent exercise (I'm not talking about incidental activity, I'm talking about actual structured, regular workouts).
We all intend to do it, and while some of us do, most of us don't.

Research and simple observation tells us that the vast majority of us spend a great deal of our adult lives starting and stopping exercise or activity programs. Very few people start and maintain structured exercise programs for the long term.
We perpetually talk about it, but we don't do it (for a range of reasons).

We join gyms, we don't go.
We start running programs, we last a week.
We buy a treadmill, we hang washing on it.
We get ourselves a mountain bike, we ride it twice.
We buy cross-trainers, we don't even know what cross-training is.
You know the drill; your story may be slightly different, but you know exactly what I'm talking about.

So after watching thousands of people struggle with their exercise goals over way too many years, I have a few ideas on the matter and a few suggestions for you if your goal is to create a better body forever.
If you're someone who has a history of 'almost' getting in shape and you've started and stopped more programs than you care to remember, then you'll probably find the following interesting and helpful.

1. Start (and progress) realistically.
As obvious and simple as this sounds, many people don't do it. Some people, often blokes with massive egos (so I've heard) will attempt to go from lounge lizard to Olympic athlete in four days. Spare your hamstrings my silly, deluded brethren, save yourself some embarrassment and humiliation and spend at least four to eight weeks creating a reasonable strength and fitness base before you get too Olympian on us.
Slow and steady Tiger... it's not about the next four weeks; it's about the next four decades.

2. Collect some base-line data and set some goals.
It's always great to take some 'before' measurements to give us some perspective on our progress over time (it's very hard for you to be objective when it comes to... you). Set yourself some physiological goals (girth measurements, weight, blood pressure), some fitness goals (aerobic capacity, strength, flexibility), some behavioural goals ("I will walk to work daily"), possibly a sporting goal or two ("I will run a half marathon this year"), maybe some competitive goals ("I will beat my brother at tennis by July") and possibly some personal achievement goals ("I will climb Mount Everest in the next three years").
You get the idea.
Goals help us create momentum and keep doing what we need to do.

3. Take some photos every four weeks.
Don't we love semi-nude pictures of our pudgy, out-of-shape bodies?
The one sure-fire consequence of a few front, side and rear photos of yourself in the 'almost-buff'... is a reality check.
Yes, we hate it, no we don't wanna see it, but sometimes it's enough to jolt us into action.
Sometimes a little in-yer-face reality is what we need.
The regular photo is a great way to get absolute perspective of your progress.
Wear the same clothes at the same time of day in the same room for each photo (if possible).

4. Variety.
When it comes to your training, variety is crucial if you (1) want to keep your body adapting (remember; different creates different) and (2) don't want to die of boredom by week six.
Your body needs it and your head needs it; so mix it up.
Variety increases the enjoyment factor, program adherence, the speed and quality of results and decreases the likelihood of injury.
Unless, of course, one of those training options is bull fighting.

5.Make it fun.
The more we enjoy the process, the more likely we are to stay on track and get the job done. Sometimes we just need to get a little hard-core and simply tough it out .. but whenever it's possible we should choose an exercise, activity or sport that will get us where we want to go (with our body) and also let us enjoy (most of) the process.
If, for example, you find jogging mind-numbingly boring and unenjoyable but you love tennis... then go and find your racquet... running for a reason!

6. Get involved in social sport, become a member of a team.
Not for everyone this suggestion but for many, it's a winner.
Hanging out and playing sport with some of your friends means the double benefit; improved fitness along with some fun and socialising.. which in turn means you're more likely to do it for longer. Unless of course it all gets a little serious on the volleyball court and you end up screaming at your buddies over a 'fun' game.

7. Work in four week blocks.
Sometimes the concept of 'forever' change (that is, changing exercise behaviours for the next fifty years) can be a little daunting.
So it's great to have short, medium and long term goals and thinking when it comes to changing your exercise habits.
Four weeks is short enough to get your head around (and keep it there) but also long enough to create some genuine change. Incorporate some of your goal setting around these four week blocks ("I will drop 8 pounds in the next 28 days and I will walk for one hour every morning").

8. Have regular re-assessments.
Like the photos, the regular re-assessments are a great way to gauge your progress and the value of the program you're following... and also good for a reality check. If you're doing everything 'right', then you should see some significant change with each re-assessment.
These testing sessions can be wrapped nicely around your four week blocks.
A typical re-assessment may involve both fitness testing (strength, aerobic capacity, etc.) and / or physical measurements.
This regular type of testing will also help you determine whether or not your exercise program needs to be modified or adapted in some way.

9. Have a practical plan and approach and de-emotionalise the process.
When it comes to our body and exercise in general, too many of us are irrational, emotional and inconsistent. Many of us exercise with no real strategy, plan or logic; we just go nuts for three weeks (with exercise), tear our calf muscle and then do nothing for six months.

The hit and miss training philosophy doesn't work... but many of us employ it.

We don't want to be obsessed, but we do want to be organised, structured and logical about our exercise if we are serious about creating forever results.

10. Keep an exercise diary.
Keeping a record of our exercise serves a few purposes:

1) It helps us stay disciplined and in touch with reality.
2) It increases our awareness and understanding of how our body responds to exercise.
3) It helps keep us motivated and interested in our training.
4) It gives us perspective on the whole process; being able to read over the last three months of work (for eg.) gives us a sense of achievement and a realistic (un-emotional) insight into our progress.
5) It helps us stay accountable... and doing what we need to do.

11. Get yourself a training partner.
Having a training partner is (for many) an effective staying-on-track strategy.
Going through the process with someone who's in a similar place to you makes sense and generally means greater exercise adherence (what we want).
The fun factor increases, you'll enjoy the process more and before you know it, exercise will be a habit.

12. Use a Personal Trainer . . . even for a while.
For some people this is a sensible and practical (but not necessarily cheap) option.
A quality Trainer will motivate you, educate you, kick you in the pants and keep you honest.
If you can do it without a Trainer, even better.
Even though I own a Personal Training business, I don't always believe that using a Trainer is the best option... but for some people having an appointment with a fitness professional is what works.

13. Create some non-negotiable exercise rules.
While most of us start with a rush, the truth is that many of us lose motivation, focus and momentum within as little as a week, that's why we need non-negotiable, I-will-do-this-no-matter-what rules. We know that motivation comes and goes, so we need something which is set in stone: "I will exercise five days per week, no matter what."... "I will jog three mornings per week... even when I don't feel like it."

14. Stop moving the goal posts.
Once you get there (reach your goal) allow yourself to enjoy what you've achieved.
So many people lose the weight, gain the muscle, drop the fat and then get themselves into this 'state' of never being fit enough, skinny enough or buffed enough.
They create another problem.
Sometimes it's okay to enjoy your body and simply 'maintain'.

Well, there you have it; exercise adherence 101.

If you have a history of getting on and off the fitness merry-go-round then perhaps today might be the day you re-write history.

If you choose to.

Author's Bio: 

Craig Harper (B.Ex.Sci.) is an Australian motivational speaker, qualified exercise scientist, author, columnist, radio presenter, television host and owner of one of the largest personal training centres in the world.

He can be heard weekly on Australian Radio SEN 1116 and GOLD FM and appears on Australian television on Channel 31's 'Living Life Now' and Network Ten's '9AM'.

Motivational Speaker - Craig Harper