Outside the POV of religion, would suicide still be wrong?

I’m assuming most of us know what some religions think about suicide. That only God could take our human lives and never by our own hands. I don’t know what Buddhism thinks about suicides. But taking religion out of the discussion, would you think that a human being taking his own life is wrong? If it is not wrong, then why would it be right?

I am also not just talking about suicide induced by extreme physical or emotional pain, this is also about the possibility of a human being becoming simply disinterested or tired with experiencing human life and making the decision to “shut himself down.”