OK, I wanted to write this a little while ago; but here goes;
[Disclaimer- Those involved in psychology and addiction recovery, as well as Jewish scholars of all time agree that it's a good idea to treat a persons inclination towards evil in 'human' terms.]
There is a little person, around all the time- הוא השטן הוא יצר הרע הוא מלאך המות. Always trying to make us sin. One big way he does that -especially to me- recently, is trying to make one concentrate on one's past, especially the negative aspects thereof. For me; how I wasted my life for four years in Yeshiva. It eats at me all the time. 23-24 starting college?! Maybe try for a Masters. So I'll be eligible for marriage at 30?! But again, first of all, going to yeshiva is a very good thing for many, many reasons (even though they probably learn more in monasteries, madrases and Buddhist temples). Secondly; it's of UTMOST importance to remember that you can't change what happened in the past now, all you can change is what happens in the future.
So there Satan!