First, I want to state clearly that I don't ever want to give anyone a reason or rationalization or encouragement of any kind, to kill themselves (well, maybe Ryan Seacrest - go for it, buddy). Suicide has consequences on those around you, and even it it didn't, hell, what's one more day, you can get through that, can't you? And every day it's the same, you can still ask that same question, just one more day...so, there's really no good reason to off yourself today.
Actually, considering suicide as an option can give you the means to carry on, as it let's you know there's a way out if it comes to that. I don't know how many times I've said "Well, I can always kill myself." Having the courage to actually do it is another thing, as is the means to carry it out. I mean, it would seem easy enough, really, and I once found it odd that someone had to write an instruction manual (Final Exit) so people would know what to do, but it does take some thought. Hell, even jumping off a bridge is no guarantee (many people have survived bridge jumps and lived to regret it).
Roger Ebert once reported that Woody Allen told him in a conversation that not one day went by that he didn't seriously consider suicide. When I first read that, I thought That's me!, because that was me for a long time. Not anymore, because even if this life is all we've got (and especially if it is) it has things to offer. Even if your life sucks most of the time, why not hang around to see what happens next? I mean, it's not like you're going to live forever anyway, is it? Plus, being slightly suicidal all the time gives you an advantage over all the fools who constantly lament how short life is, because you can focus on living and not really give a damn (too much) about dying.
Atheists are sometimes asked, "If everything is so meaningless, why not just kill yourself?" But why should I? I'm alive now, someday I'll be dead, and in the meantime, I've got a whole world of idiots to entertain me while I'm waiting.
So the question again is, have YOU ever considered killing yourself, and if so, why?