Here is an experience that I often have: I'm walking down the street, perfectly content and all of a sudden some memory pops into my stream of consciousness. The memory triggers some past circumstance where I did not act completely admirably. Immediately following this, there is often regret. Regret of the form like: "I should've studied harder for that class", "I should've researched my options better before choosing my college", "I should've asked that girl out", "I shouldn't have been such an asshole to her" and so on. So this is regret which is of the kind: "Well, of course, I should've done X. But I did Y. And now here I am."
This is classic hindsight bias. Looking back into the past, it seems clear what my course of action should've been. But it wasn't at all that clear in the past.
So, I've come up with a technique to attenuate this kind of hindsight-bias driven regret.
First of all, tune in to your current experience. What is it like to be here, right here and right now, doing the things you're doing. Start zooming out: think about the future and what you're going to be doing tomorrow, next week, next month, next year, 5 years later. Is it at all clear what choices you should make? Sure, you have some hints: take care of your health, save money, maybe work harder at your job. But nothing very specific. Tune in to the difficulties of carrying out even definitely good things. You told yourself that you'd definitely go running today, but you didn't. In first-person mode, it is really hard to know what do, to know how to do it and to actually do it.
Now, think back to the person you were in the past, when you made the choices that you're regretting. Try to imagine the particular place and time when you made that choice. Try to feel into what it was like. Try to color in the details: the ambient lighting of the room, the clothes you and others were wearing, the sounds and the smells. Try to feel into what was going on in your mind. Usually it turns out that you were confused and pulled in many different directions and, all said and done, you had to make a choice and you made one.
Now realize that back then you were facing exactly the kinds of uncertainties and confusions you are feeling now. In the first-person view there are no certainties; there are only half-baked ideas, hunches, gut feelings, mish-mash theories floating in your head, fragments of things you read and heard in different places.
Now think back to the regrettable decision you made. Is it fair to hold that decision against yourself which such moral force?