Is that the green monster I spot lurking over there?

Why is it, that no matter how happy you are, there always seems to be that one thing/person/ annoying voice in your head, that tries to ruin it? I mean, it cant be human nature, or else we'd all be wiped out by now because everyone would be stopping each other's happiness and thus, stopping the love going on... Animal instinct maybe? Like in a pride there's only one alpha, and he gets a choice of who he wants, but then there's always the other male lions wanting to be alpha, or having different lioness' so then the alpha decides he wants a different lioness or something? (You wont get this, Its just for me to try and make sense of it, unless you have amazing logic like me ;D) Or, is it that we all just think that people are trying to ruin things for us? Are we, in being paranoid about everyone else trying to ruin us, really ruining  it ourselves? Maybe I am just being paranoid... Maybe I just don't want to lose *... Maybe *'s found someone better? Someone (that reminds me of a pervy pirate) that can understand * better... (If you haven't guessed, I'm using * as a substitute for a name) Maybe I'm the one ruining it? With my incessant pangs of jealousy? I really don't know anymore, but * seems happier with this other person, maybe I should stop getting in the way of them... See what would happen if I left the picture or something? But then, I'm a selfish person, I don't want to do this unless I really have no other choice or no other way of knowing. Eugh, see what voices in head do to you -.- they change your perception of Everything! I never used to worry, or want to be in a... Commitment, but now I worry constantly that I'm not good enough and that this commitment might just be over because of me. -.- Things aren't looking too good at the moment :L <3