I agree with Swany, that it would be rather risky to start changing things. The linear timeline is the way things should be. To start tampering with that, is essentially erasing your destined future. I believe in a certain destiny, and I want to find out what it is too. I'll use the cheat codes after I've played the whole game without them.
Having that said, against my better judgment I'm tempted to go back and reverse a few mistakes I've made. I know that we're people, and that we make mistakes all the time, but the consequences still suck.
I think I could learn a few things from my past self. Such as drive and determination. Disappointment, and especially having to accept it kills off your hunger, you know. Sometimes I wish I had the hunger I had then. I could accomplish a lot more that way, I think. I just don't know how to get it back, heh.
I don't think I could teach my past self any self-confidence. Self-confidence comes with experience while growing up, you can't tell a person to have self-confidence; they have to live it to get it.
I'm curious to see what my future self would be like. If it's any good, I'd definitely have more faith in things. If it's bad, well that would suck. I'd seriously reconsider my temperal prime directive, heh.
I always try not to look into the future too much. There is no telling what things are going to be like anyways.