How do you burn out completely one's past karma in this present life itself?

Our past karma gets burnt out automatically, the moment we experience its result in present life.
Everything that we see and experience in life through the five senses is the result of our past karma.
The law of karma is such that whatever seeds of karma we have sown in our past life, we HAVE to bear the fruits of it in the present life. When the time is up for maturation of karma, our past karma automatically comes into effect, gives the effect, and gets discharged (burnt out) naturally on its own.

But while experiencing the effect of past karma, we simultaneously bind new karma for next lifer
This present life is the result of past life and the cause of the next life. Param Pujya Dada Bhagwan explains this relationship, “Seeds (of karma) sown in the previous life, result into a plant in this life. When we sow a seed of wheat, that’s the past life; and the plant which grows from it is this present life. Now from this plant, the new seeds that fall (get sown), will grow as a plant in the new life.”

For instance, when someone happens to insult us, it is the result of our past karma. The seed of insult that we’d sown in previous life has got ready to bear fruit today in this present life. However, we forget that ‘the other person’s action is merely on account of my own past karma. In past life, I myself have sown this karma of insult.’ And today, when this person is merely delivering the fruit of our past karma, we hold him responsible; and maybe even insult him badly in return.

Now, if we could have remained calm and equanimous, this past karma of insult would burn out completely in its natural process, and it would have been an end of story. However, rather than seeing our own past karma, we saw the other person as guilty; and in turn reacted by way of anger. This creates a new karma (seed that would now grow again in the next life), the result of which we will have to experience in the next life. It was already difficult to tolerate this ‘one’ insult, and yet, out of ignorance, we chose to continue the series of insults by throwing it back at the other person. We further multiplied the karma by seeing the person guilty, who in fact helped us in the process of our past karma to burn out completely.

So, if we understand the theory of karma in exactness, there remains no reason to accuse anyone. It is only due to our wrong understanding that we get puzzled and confused that why is there so much of suffering in my life?! Try asking your neighbour to verbally abuse you every morning. He would shrug his shoulders and say, “why should I?” This proves that we encounter suffering only if there exists a past karma (a fault of ours), not otherwise.

However, if we ask for forgiveness and vow not to repeat the mistake again, that new karma will be erased immediately. Suppose we write a letter to our close friend, wherein we made a mistake. Now, changes in this letter are possible only until it has not been mailed. Once the letter is mailed i.e. we die in this present life, it remains no longer in our hands to make any change. The karma gets bound (caused) then. Thus, we can erase all the mistakes we’ve made in this present life by doing pratikraman (seek pardon), before we leave this body and move into the next life.
The key reasons for charging of new Karma are:
1.Our inner intent at the time when our past karma is unfolding, and
2.At the root, the ignorance of the Self.

Our intention is what binds new karma, and not our actions.
Our past karmas that manifest in our present life are the 'echoes' of our previous intentions. But we can reverse these wrong intentions by doing pratikraman before whichever God we believe in.
Pratikraman is done through the following 3 steps:

• Alochana (the process of heartily recalling or confessing our wrong intentions or actions),
• Pratikraman (asking for sincere apology with repentance for all our wrongdoings), and
• Pratyakhyan (resolve never to repeat these mistakes).
For example, a butcher, owing to his past karma, may be killing animals to sustain his family in this present life. But from within, he is regretting this action of killing and constantly doing pratikraman. Doing so, inspite of killing animals in present life, he ends up burning out his past karma, and in turn, with his good intent, binds merit karmas for future life.

Now on the other hand, seeing this butcher, a passer-by curses him from within, wishing that he should be hung to death for killing innocent animals. This person binds demerit karmas and invites suffering into his future life. This is how the law of karma operates.

So, if we do not like suffering, we should always maintain a deep inner intent, ‘May no living being be caused the slightest hurt through my thoughts, speech and actions.’ When we intend giving the slightest pain to any living being, that karma will give us its fruit in the form of pain to that extent.

The main cause of karma is the ignorance of the Selfr
Param Pujya Dadashri says,
“Once you come into the nature of the Self, no new karma will bind. This happens when Gnani makes you aware of your own real Self. After that, new karmas do not bind and old karmas continue to discharge. When all the karmas have discharged, you attain final liberation.”

Through Akram Vignan, the stepless path to Self-Realization, we can discover our real Self (the Pure Soul within) with the grace of Akram Gnani, in a 2-hour scientific process of Self-Realization. We herein obtain the right vision through which we can see the world as flawless (without any fault). The feeling of taking revenge does not remain after Self-Realization and exact pratikraman also begins only thereafter.

So come, let’s attai
Self-Realization from the Living Gnani, and with His loving guidance, learn to remain in the awareness of, really I am not Chandu (please insert your own name here), I am a Pure Soul.’ This shall help us burn out all our past karmas completely, with a smile on our face ï and equanimity in our heart, so that we secure our ultimate liberation!

To know more: https://www.dadabhagwan.org/path-to-happiness/spiritual-science/the-science-of-karma/