I had a rough time growing up in a number of dimensions. The end result was for the longest time, I did not like me, because I had been so hurt and I blamed myself (as children do) for my misfortune. During that time, I often thought of suicide.
When I got older, I started discovering who I am, but I spent a long time very lost within myself because I did not have an accurate self concept. During that time, I often thought of suicide as well.
As I got even older, I fully realized who I am and that I quite like who I am in a very quiet and serene way. At that point, I never again thought of suicide, even when things were really bad.
What did it for me was not necessarily a lack of strength, cowardice, or any other failing. It was a lack of accuracy in my point of view, which caused me to get all mixed up on a number of dimensions. Depression can be like that. Its not necessarily failing to meet a challenge, but more of the result of confusion which causes a different kind of despair.