Stoics don’t trust pleasure. Here’s Seneca summarizing Stoicism:

Cling tooth and nail to the following rule: Not to give in to adversity, never to trust prosperity, and always to take full note of fortune’s habit of behaving just as she pleases, treating her as if she were actually going to do everything it is in her power to do.

And here’s Marcus Aurelius:

The soul does violence to itself when it is overpowered by pleasure.

Why not trust pleasure?

The chasing of pleasure can lead to ruin. This is obvious in the case of the addict. What begins as an ecstatic pursuit becomes boring and often turns tragic. Addicts experience more of the downsides of drugs and less of the upside as they build a tolerance.

Of course, not every pleasure leads to ruin. Many experiences are fantastic. But what we crave may come back to bite us.

The neurological basis for this is becoming clearer. In her book Never Enough, Judith Grisel notes that biological systems tend maintain homeostasis. That is, they are constantly updating to remain stable in the face of new stimuli. You can see this with caffeine. As you ingest caffeine more frequently, you’ll build a tolerance. Caffeine will no longer have the power that it once did. Your body will acclimate to it. Grisel notes:

The terrible truth for all those who love mind-altering chemicals is that if the chemicals are used with regularity, the brain always adapts to compensate. An addict doesn’t drink coffee because she is tired; she is tired because she drinks coffee. Regular drinkers don’t have cocktails in order to relax after a rough day; their day is filled with tension and anxiety because they drink so much.

On Grisel’s account this is because the brain seeks homeostasis. Every time we ingest a drug, the brain will facilitate the opposite state. Ingesting a opioids will bring about an opioid infused state, but will also kick off a process releasing anti-opiates. For this reason, opiates are particularly unpleasant:

One way to understand the dilemma of the opiate user is to recognize that because there are no free lunches, the benefits that drugs confer will have to be paid back. In principle, moments of superb contentment demand an equal and opposite experience of distress; the benefit of euphoria will create a debt of dysphoria; and trying to avoid this unpleasant state by taking more drug will just increase what you owe.

This dynamic is not just a feature of drug experiences. Consider falling in love. At first, falling in love is new, euphoric. Overtime, spending time with your partner becomes the new normal. However, if your partner leaves the result can be heartbreak and pain. It takes time to return back to your original state.

This does not mean that pleasure is not to be pursued. However, it does show the wisdom of moderation. Going overboard results in building a tolerance and withdrawal. Prosperity is wonderful — but do not lose yourself in it.

This dynamic also reveals why it can make sense to undergo unpleasant experiences.

If you want to achieve a sustained positive state, you could submit yourself to negatively charged experiences. This way the opponent process would be positive…Jumping out of an airplane at several thousand feet produces intense feelings of arousal and panic, even feelings associated with impending death. They would probably last for much of the air time and certainly for all of the “free fall.” As the stimulus ends and your feet are miraculously back on solid ground, not only is the panic gone, but according to hobbyists it is like being awash in feelings of extreme calm and well-being. The relief following an intensely stressful experience, if you live through the event, may make it all worthwhile.

This thought is behind many Stoic gratitude exercises. Imagining that we’ve lost what we treasure helps us value what we have now. Undergoing voluntary discomfort kicks off opponent processes that can result in more joy. The Stoics realized that we could hack our brains tendency to maintain homeostasis, by injecting unpleasant activities into our life, we can sustain positive states.

As a general rule then, be wary of too much pleasure seeking.

In the end, the very effect I loved so much about alcohol — its ability to mute existential fears — utterly betrayed me. It didn’t take all that long before the drug’s most reliable effect was to ensure the alienation, despair, and emptiness that I sought to medicate.