I have somewhat mixed feelings on this subject. While I'm not very religious, part of me believes that things happen for a reason. There have been very close calls in my life where things were at the edge of going overboard, but one simple thing changed everything.
However, I also strongly believe in something my favorite teacher used to quote. She always said, "Life is 5% what happens and 95% how you react to it." Sure, there are some things that are completely beyond your control, but depending on how you chose to react to those things can altar your life. For instance, let's say a friend started some vicious rumor about me. There are tons of ways I can chose to resolve this. I could start a rumor back, which could potentially start a rumor war-- this could change the way people look at me. I could get in a fight, which could potentally get me suspended and change the colleges that may or may not accept me if it happens other times. I could try to talk to the rumor starter about it, but that could end various ways. I could do nothing, and try to get it to pass over. If I take it badly enough, I could kill myself. If I try to be optimistic, I could better myself and try to show that I'm better off anyways. I could let it make me paranoid about who I chose as friends. And I could talk myself out of any one of these options and into another.
So while destiny may have some ultimate future I may acquire, it's the choices I make that will lead me to it.