Revel in your nature as a chemical reaction

ATP is decomposed into ADP and a neuron generates enough energy to metabolize tryptophan into serotonin. Acetylcholine released by a few surrounding axons hits the neuron's dendrites all at once, opening enough ion channels to send a lightning-fast action potential down the cell body. The depolarization from the action potential forces vesicles to release the serotonin they have stored up, flooding the surrounding brain area. Your eyes close and you smile because your friend's hug feels so fucking good. You are beautiful chaos, stunningly complex chemistry in action, emergent behavior from simply described reactions.

When you look at yourself this way everything becomes a lot clearer. No longer are your mood swings something to blame on yourself, some kind of cognitive mistake. Now they're simply a side reaction gone wrong -- too much or too little of some neurotransmitter in some area -- easily fixed by making enough of that chemical available to let the reaction proceed in a normal way. When your stomach burns with indigestion, add enough basic material to bring the acidic content back down to where it should be. Of course the doctors are confident the pills will always win, the pills are manipulating your "self" on it's lowest level, instead of a higher, more conscious one. Sort of like wearing lenses if you're near-sighted, you're just finding the most elegant solution to a fundamentally low-level problem.

True solipsism lets you take this as far as you want, and pursue satisfaction (and gratification, and joy) through the manipulation of your own chemical reaction, the only thing that you know positively to be real. You seek out foods that make the neurons connected to your taste buds fire in novel and interesting patterns. You take a long, hot bath that quickens lactic acid metabolism in your muscles, easing the day's aches and pains. You ingest chemicals that force a normal reaction to proceed in an abnormal way, bending your perception and letting you see reality in a radically different light. Perhaps, if you will it or accidentally make a miscalculation, you change your reaction in such a way that it can no longer sustain itself, and you die. You are free -- or at least you should be -- to do whatever you want with the reagents, catalysts and precursors that you're made up of.

Take joy from your freedom.

I know now that I'm older that this is wishful thinking, but I still don't understand how it's possible for you to feel so strongly for another person while they only feel indifference to you. You can't believe that another can use you merely to satisfy his lust if you are in love with him. Things shouldn't work this way...if there were any order in the universe, it wouldn't. And as a result you see things as being without meaning, the symbolic relationships that you've always tried to draw between people, objects, and ideas, clear lines that connect things and provide order to the universe disappear. Delusions of an active imagination, magical thinking. You are forced to look at the world with cold logic, laws of physics and biology, realizing yourself to be a creature controlled by chemicals reacting. A lack of certain chemicals cause this ache, this emptiness in your soul and certain hormones released by touching another cause you to yearn. These emotions that you feel are biological illusions, love, as said by the devil, is biochemically no different from eating large quantities of chocolate.

You rebel against this in your mind, you wish to believe that there is something more meaningful. You want a reason to feel as you do, you want your tears to have more than a biological basis as well as your joy. Then you realize this rebellion isn't your own, it too belongs to the chemicals, and you throw up your hands, you are back to square one.