Man is that so this so true. The same happened to me and, of course, when your 'happiness' it taken from you (you get dumped), you tend to beg and plead for it back. Been there done that. Luckily, I have been able to figure this out as you have. I have re-connected with the person I was before we were together. I look at the person I became in the relationship and just can't believe I allowed my self to fall so far into the same 'depression' you refer to. I have cut out all of those bad habits and have re-established a confidence in myself that has been gone for a long time. Today, I can honestly say I am a better me. It sucks it had to happen the way it did, but the fact is it had to happen. I have goals and I'm actively pursuing them as well. I evaluated the way I handle my personal relationships and today I am a better friend, son, brother, etc. to the people in my life. If you were worth leaving at the time, a break up should be a wake up call for you.