Eight affirmations for regret — for the road not taken, the years you think you wasted, and making peace with choices you cannot unmake.

Regret is the only feeling that requires time travel to satisfy. Every other emotion has something you can do about it. Regret asks for a different past, which is the one request the universe has never once granted.
These ten affirmations are about setting the demand down. Not deciding the choice was secretly fine — some choices were genuinely bad — but ending the arrangement where you serve a sentence for it indefinitely.
Say one line, then do the smallest thing the regret is pointing at. Regret usually contains information: it names a value you did not act on. Acting on that value now is the only functioning form of repair available.
Then be specific with yourself about what you actually knew at the time. Regret runs on hindsight and quietly credits your past self with information they did not have, which is what makes the verdict so unfairly harsh.

1. “I make peace with myself and my past.”

2. “I make peace with each of my mistakes because they are in the past.”

3. “I am at peace with my past choices.”

4. “I am at peace with my past decisions.”

5. “I allow myself to be at peace with my past.”

6. “I forgive myself for past errors.”

7. “I make peace with each of my mistakes.”

8. “I choose to forgive myself for past mistakes.”
Give the regret a job. It is pointing at something you value; act on that value now, in some small way. Regret without an outlet loops, and regret with an action attached tends to quieten.
Briefly, yes — it is one of the ways people learn what matters to them. It stops being useful when it becomes a permanent sentence rather than a lesson you have already taken.
"I am at peace with my past choices." It will feel untrue at first; say it anyway. Peace with the past is built by repetition rather than by finally winning the argument.
The same way you would forgive anyone: account for what you actually knew at the time, acknowledge the harm honestly, and then stop charging interest. The last part is the one most people skip.