I was severely depressed and suicidal in my teens and again severely depressed in my early 20s. Once I learned how selfish suicide is, I put it off. But still in my college days, I would materialize a gun in my mind every single day and shooting my brains out. At the time I thought it was just a thing that happened while studying, but later on when those visions stopped, I realized just how depressed I was.
I never did take meds or therapy, and I never told anyone about it until after the fact. But these things can help.
I enjoy life a lot now, but I am always working on enjoying it more.