Suicide reflects the seriously inadequate development of those basic ego capacities governing a sturdy sense of self (sense of who one is), modulation of affect, and control over thinking and behavior. This causes profound feelings of worthlessness and, when exacerbated by an immediate stress, suicidal behavior may result.
Thus, a teenager doesn't suicide simply because they broke up with their boy/girl friend, and most recent soldiers who committed suicide never saw combat with many never even having left the USA.
Alcoholism and drug abuse reflect the attempted self-medication of emotional deficiencies. It's not easy to kill oneself, living being a biological imperative, unless one momentarily lacks self-control because of drugs or alcohol use. To paraphrase F. Scott Fitzgerald, 3AM is the darkest time of the day. Nelson Algren attempted suicide after the failure of his first novel in 1935. Fourteen years later he won the National Book Award for The Man With the Golden Arm.