Have you thought of an action or moment where you have thought that I shouldn't have done that or I should have done that, I would have and I could have achieved it.... You are living in the shoulda, woulda, coulda land. I experienced it myself and it is difficult to be reliving those moments because there is no solution to it. There is no going back. 

Shoulda, woulda, coulda according to Urban Dictionary, " it is of no use to dwell on what is or what should have, could have or would have happened/been done." Pretty much living in the world of regret. It is not the greatest feeling at all. There are ways to combat that. We have to remember that we have our past and we have made mistakes but how we view every decisions we make should not make us an inhabitant of the shoulda, woulda, coulda land.