In summary, what the Bhagavad Gita says about karma is that every action we take has an effect or a result, and we subsequently reap the benefits or drawbacks of our actions. To be united with any action as in ‘I am doing’, will incur an effect. Effects will follow one into their future life.
Now, let’s consider your question about helping those who have helped you and if we don’t, will their Soul follow us into the next life? Or will our overall help be taken into account?
As for the same Soul, there is no guarantee that we will have to help the same Soul in return in the next life. We may or may not meet the same person in our next life. But yes, your deeds will, with certainty, follow you into your next life. Every single deed, good and bad, has to be paid off respectively.
Understanding the science behind binding karma.
The common belief of karma is that our visible actions bind us. But the binding of karmas is determined by intention rather than action. Good karma is bound by the intention of giving happiness to others, while bad karma is bound by the intention of hurting others. The external actions in themselves are not what binds karma; it is the inner intent that causes the bondage of karma. Therefore, it is important to be aware of our inner intent and avoid negative intentions.
If someone has helped us in any way, be it financially or otherwise, it is important to have the intention of returning the favor whenever the opportunity arises. Nevertheless, if someone has lent us money, we should have an intent to repay it on priority, as soon as possible. Rest is in the hands of Nature; at the appropriate time, it will help us help people and also appropriately return their help.
What follows us into our next life are our emotions, that of anger, pride, deceit, greed, attachment, and abhorrence (kashays). For example, helping someone is a result of your past life causes and while helping them, whatever you feel within is what counts. If for example, an intent is motivated by selfish interest, it will bind demerit karma. Conversely, if there is no selfish intent, merit karma will be bound. So, if you are sincere in your intentions of returning the favour, this will be taken into account. Regardless, karmas are still bound and thereby perpetual cycles of births and rebirth.
The essence of 'The Gita’ explained!
Before the great war of the Mahabharat Shri Krishna said to Arjun,
"Arjun, you have been with me for a long time, but still you haven't known me in the true sense. What you see in front of you is not the real me; what you see is the physical body. I am separate from this body. I am a Pure Soul. You too, are a Pure Soul. Your brothers, uncles, gurus, and friends with whom you are about to fight, are also Pure Souls. This (fighting) is your destiny (karma), so you have to carry it out with this awareness of the Soul. If you remain in this awareness and fight the war, you will not bind any new karmas and your remaining ones will be exhausted. This will lead you to ultimate salvation."
The knowledge that Lord Krishna gave to Arjun verily is what we can get today through the Akram Vignan path.
Here, Gnani Purush destroys our deluding karma of countless past lives and gives us the right vision that gets permanently established in us, such that we start seeing the Self (the Pure Soul) in everyone (‘Aatmavat Sarva Bhuteshu’). On the Akram path, this is done through a Self-realisation ceremony called Gnan Vidhi, conducted by the Enlightened Gnani. He gives us the awareness of the Self and the right understanding of who is the doer in this world. Thereafter, we get onto the path that leads us to ultimate salvation, after which there will be no next life at all.
Ambalal M. Patel was a civil contractor by profession. In June 1958, spontaneous Self-Realization occurred within Ambalal M. Patel. From this point on, Ambalal became a Gnani Purush, and the Lord that manifested within him became known as Dada Bhagwan. A Gnani Purush is One who has realized the Self and is able to help others do the same. Param Pujya Dada Bhagwan used to go from town to town and country-to-country to give satsang (spiritual discourse) and impart the knowledge of the Self, as well as knowledge of harmonious worldly interactions to everyone who came to meet him. This spiritual science, known as Akram Vignan, is the step-less path to Self-realization.