Karl mentioned on a comment on his blog a while back how wonderful it would be to have a self-help book written specifically for pessimists like us (paraphrase). If anyone actually wants instant sainthood in my eyes by creating such a book (a bible, if you will), I'll start the ball rolling and help you out a bit.
METHOD 1 See psychiatrist (legal drug-dealer), get some meds, become a good slave
Taking medication isn't the same thing as admitting you're wrong about life. It could just as easily be a way of saying "the world is so unbelievably bad I have to change my entire brain to deal with it". If you can't, for reasons such as living in a place with no national healthcare service, you can try a number of natural antidepressants and nootropics. But wait, what if it's just a placebo effect! Placebo effect, Shmacebo effect. I would eat goat testicles everyday if it tricked my bastard brain into thinking the world isn't such a festering pile of corpse chunks marinated with sweat, blood and tears. And it kept me non-deluded enough, of course, to remember that bringing a kid into this world is a big no-no. You see, I think getting through life un-suicidal is a fragile balance between knowing the truth, and hypnotising yourself into thinking you are a mindless chicken. You can't be so happy you'll do something you'll regret, and you can't be so depressed you'll do something you would regret if you wouldn't be dead and without emotions after it. This goes back, I think, to this.
METHOD 2 Emotions don't have to be an accurate representation of reality
Stephen King, pssh. H.P Lovecraft? No. Ligotti? Getting warmer but still far off the mark. The greatest horror writer in this universe is actually the universe itself. And if you know that, you can help yourself a bit by not having kids, being nice to other people bla bla bla, but ultimately, going around, paralysed with fear is just going to make your loved ones worry (if you are unlucky enough to have them and are therefore unable to commit suicide). Realise that though happiness is impossible to obtain without, again, decades of meditation or years of medication, you don't have to hurt yourself even more by subtly changing your emotions to fit your circumstances. Life sucks. Though it may help to keep saying that in the short term, in the long term you are causing your brain to slowly wither away into a fortress of pain. If you find yourself despising being trapped inside the worst prison imaginable, simply mentally scream 'La la la I'm not listening', and pretend you live inside clouds, or your mind is a haven from the outside universe, or even that the future will be a brilliant place. (Note: I doubt these will work. If they do work, you also run into the danger of losing a sense of the truth of the matter. Catch-22 situation)
METHOD 3 Become a hedonist and let loose
I don't know how this works. I see people partying and taking drugs and things, and they seem to be having a good time.
METHOD 4 Meditate until you are basically dead, then wait for death
Losing your sense of self, concentrating on the present, stopping all thought. These things, to me, seem like a way to die before you actually die. But science says meditation works, so it must work*. Also for those of us who just can't get enough of death, I'm supposing that despite how losing your desire seems a little boring, being a zombie who can't get enough of mindfulness might really stop a lot of those annoying 'WORLD SUCKS SO BAD' thoughts. And the real up-side of Buddhism is, it is still pessimistic, to an extent.
METHOD 5 Focus on some goals. Complete them. Make more.
Self-explanatory. Can help more for those who are anhedonic, in my experience, though it is still bloody annoying (an understatement).
METHOD 6 Escapism
For those of us who can still feel interest and other such positive emotions, rather than simply the absence of pain, then I suggest you live in fantasy worlds instead of this horrible one. With the vast amount of media out there, this really, really isn't hard.
So there you have it, a bare bones guide to living life despite understanding life. Please, for the sake of all us denizens who lurk among these plains, enhance it and do me proud.
*XTC's 'Making Plans for Nigel' played here. I don't know why.