Excitism is the belief that one can more effectively work spells when one is in an excited state.
Excitement generally consists of 1) anger/hate, 2) pain, 3) anguish/grief, 4) shame/embarassment, 5) surprise/shock/fear.
What this means, is that excitist spellworkers can more effectively work spells if they injure themselves or are injured in heat of battle, or if they see their allies fall in battle, or see blood or explosions or corpses in general. Put them on a stage, or have something they care about put at stake, and you will get better results from them. Take them by surprise, or threaten them, and their response will be superior. In order of effectiveness, the most effective is torture, followed by rape, followed by sex, though for obvious reasons the first two do not make for good spellworking techniques. With sex, the spellworking capability of excitists spikes for a moment, during which they can cast their most impressive spells.
But when none of these things are done, they will have little or no power.
Furthermore, excitists tend to get inured to excitement as their occupational need to be subjected to such excitement means it happens too often for them. A person can only experience so much pain before they go numb from it, only self-flaggelate so much before they develop scabs. A person can only experience so much loss before hardening his spirit, and so on. Hence, excitists are most effective when young and inexperienced.