I remember once I felt something like the darkness that Bill Zeller was talking about. But I managed to just let it go. That story was really sad, but everyone is wired differently. It's hard to tell how your experiences would affect someone else. Something that would make me suicidal might seem trivial to you and vice versa. However, I think conquering your fears and your personal demons yourself can bring a great deal of satisfaction and will make you nigh indestructible if you manage to overcome them. At least make an honest effort before you have fun. And by honest effort, I mean years of trial and error of trying to find out what will improve your state of mind.
I've also found that people who are suicidal or depressed often don't appear to be in that state of mind at all. My roommate is an example. He's a cool guy and we go out and do stuff pretty often. He likes the same stuff I like and is usually in really good spirits. Then one night he was drunk and he let all of his personal shit out about how he was depressed and almost suicidal. It came as a huge shock because I never would have expected that of him. After hearing about all of these cases of seemingly normal people who are even thinking about suicide as an option, it really scares me. How many people are like this? Is it just part of being human to contemplate suicide at times? If anything, hearing about all of these cases causes me to be even more stoic and thankful that I have the fortitude to deal with life's challenges.