why does ending oneself's life must be paiful and sound terrifying???

The title is the topic. Why? I just hate not being someone I wish I were, yet I'm too coward to just do it. I really wish our physical body can just agree with our psyhcological self; I heard your body will basically do anything to keep you alive as long as possible (and that costs some agony) I hate that evolution gave us such catch-22 mechanism!