Each one of your billions of cells requires thousands of individual
atomic reactions to happen every minute for it to survive and function correctly. The definition of a
chemical reaction is multiple atomic reactions taking place in
parallel, resulting in one or more substances being changed into one or more different substances. Thus
you (the entirety of you, head to toes, mind and body) are 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.