Why its wrong to commit suicide in catholicism....?

if God know everything your gonna do in your life? Also God accuses us of committing sin even though it was done by the second human being created, just sounds like a lame excuse of why bad thing happen to humans and why the snake slithers on it belly,lol. Well i am a christian and I try to believe in God but deep down I just need proof and don't say that's why its a religion you just supposed to believe. Well that's just how God created me I guess?