Should your life be defined by the worst thing you have ever done?

There is a Blue Bloods episode where a father shoots (and doesn't kill) the man who, as a teenager, accidentally shot his daughter - who ultimately died from the shooting. Erin makes the comment something like, should your life be defined by the worst thing you have ever done?

I think we do that too often.

When I was in high school a young man killed a stranger, someone who had picked him up hitchhiking because the student wanted to steal the older man's truck. And the young man, sentenced to a life in prison, was let out after about 40 years.

More recently, one of my ex-students, in a moment of stupidity, did something that resulted in a dishonorable discharge form the service he intended to donate the rest of his life to.

My ex-classmate has returned home and is living among his former friends, attends his childhood church, and appears to have made rehabilitation.

How to help my former student see that this doesn't have to be the rest of his life - that it will not be what he planned, but he can recover?