Some good reasons already mentioned. For me health is an issue too, both physical and mental. My personal bleak situation and future. Don't really like the state of the world or where it's heading. It's bad, and most people don't seem to care or even aware (and don't mean cc). So, there's loads of things that annoy me, but nothing gets me more than the past, Minsky.
Wasn't always like this, used to be happy and don't know how life could ever be so cruel when I loved it so much. Yes, I've made mistakes, but nothing to warrant 30 years of punishment with no end in sight. Feel like my life should've been different, but somehow ended up in the wrong timeline. I've accepted it now with all it's events, good and bad, but that doesn't mean that I don't downright detest this current existence in it's very form.
Suicide, to me, is a third person perspective, if you will. As if you could see yourself suffering from Alzheimer's, what you were before and what you are now. One can't change it in that situation being the one afflicted, but I can. Didn't deserve this and will remedy it.
Maybe this sounds like self-pity, don't care. Suicide is taking care of oneself. Ending one's misery and sparing onself from more, which is why it's so wrong making it so hard on one, possibly brutal and with dire consequences, because it's not what most of us deserve.