DMT improved my outlook on life and death the most, it has made me unafraid to some extent yet I still care. (Had some issues shaking nihilism for a while though, it can be easy to take that 'putting things in perspective' stuff one step too far.)
About suicidal thoughts: well in my early days of tripping I abused the hell out of mushrooms. I didn't know how to deal with the type of experience and felt pretty tortured from time to time. Still I continued taking it because the existential crisis I had gotten myself into was lacking any relief, and desperate times call for desperate measures I guess. During the torturing trips I mentioned, every now and again the thought popped into my mind that I wanted some escape button to it all. Like jumping out of the window (which was nonsense because I lived at the 2nd floor at the time). I realized it was not a valid option and never really considered it as something I actually might do. It was mostly a signal that there was something unbearable about being that lost.
Honestly I think it is a healthy part of life to having considered all options. By that I don't mean really being actively suicidal, but realizing that this is something people may do when stuff gets so bad that absolutely everything points to a sustained situation that is unacceptable. Passive suicidal ideation tends to be a part of depression (even transient depression if something utterly shitty happens) and I think it is a natural part of life to feel utterly shitty every now and then, if only to know the full spectrum of emotion so that you can value the bright side even that much more.
Please put what I said in perspective and realize that I think active suicidal ideation should still raise all alarms and be considered a call/cry for help. Also I think people may sometimes be unable to look ahead past their depressed feelings even if realistically things can be expected to be mended. Even if essentially everyone should hold the choice to live or die themselves (IMO), it is an unimaginable shame if someone were to make that choice based on the presumption that things can't be helped... when they actually could be.
I was contacted online by a guy a few years ago, who was in a situation that sounded like permanent hell: mysophobic OCD, autism, a very painful case of scoliosis or something similar, utterly isolated and abandoned. He was absolutely terrified at the idea of his brain being infected by bacteria. He was past help apparently, the only thing "help" would do if they were contacted was drug him up and lock him up - essentially things that made it worse if anything. He asked me for methods on suicide, talking about wanting to OD on MDMA and that sort of thing. It was very hard for me to decide how to handle it ethically. I decided I would not actively aid his euthanasia but I have helped him avoid painful methods and ones bound to be unsuccessful, explaining how some things like MDMA ODing would probably be different than he imagined. He stopped contacting me around the time he planned on ending it, so best I can tell he pulled it off.
PD >> TDS
(Dear people at TDS: if you consider contacting TS (OP) to help him or her, first check his post history to evaluate credibility.
If this isn't the kind of thing suitable for TDS, feel free to undo the move)