The most useful part of regret is the change it can make in the next ordinary decision.

Regret spends most of its energy on a past that cannot be reached, replaying the moment and grading you against it. The only place it can do any work is forward, in the small decisions that resemble the one you wish you had made differently. Those chances tend to arrive in fairly unremarkable form.

Take one regret and name the everyday situation where a similar choice will come around again. Decide now what you would do. Then let the original occasion rest, since carrying it further adds nothing the decision has not already taken from it.