The Muscles of Self-Control

Exercising Self-Control
For most of my life, self-control has felt like a reservoir that drains over the course of a day. I could resist a donut in the morning, but all will was gone by the time I tried avoiding a Mountain Dew with lunch. In the short-term (like the course of day), feeling this way is normal, according to most self-control research. We experience what professional psychologists would call "ego depletion."
Fortunately however, there is evidence that self-control is like a muscle that can be strengthened over time. The idea is that the more often a person exercises their self-control, the more easily they can exert it in later tests. This is how I have reframed my thinking about self-control, and I've found it helpful. Whether trying to "exercise" self-control works or not, I have found that believing it does is enough to help me stick to my efforts, like some sort of placebo. (Placebos can still work even if we know we are taking a placebo.) Instead of thinking that "Well, I already resisted the temptation of a donut, I deserve the Mountain Dew," I reset to "If I could be strong against a donut, I can be strong against a Mountain Dew."

Testing Self-Control
The Marshmallow Test was a series of studies out of Stanford that were designed to measure the self-control of children. The test was performed giving young children a choice of a single immediate reward (a marshmallow or cookie), or a greater reward if they were able to wait at least 15 minutes. Many years later, the researchers found that the children who were able to wait for the greater reward had healthier BMIs, higher standardized test scores and had achieved higher levels of education. Other than being a test that I will try to shape my future children into responding to correctly, I find that it is a supporting piece of research that self-control can be a muscle, particularly that self-control against one temptation can cover more than a single domain. Children that can resist the immediate cookie can resist other kinds of negative temptations elsewhere in their lives.
I think that viewing self-control as a muscle is a big part of why keystone habits work. It is not just that I don't want to negate my morning's workout with a chocolate brownie after dinner, but it is because I had the self-control to go the gym that I can also skip dessert.

"Dopamine Fasting" AKA the Self-Control Superset
Dopamine fasting is a new buzzword, allegedly popular among Bay Area Yo-Pros, that is the attempt to avoid producing dopamine in the brain. The idea is that because we are constantly hearing music, having conversation, connected to the internet, eating junk food, etc. that we long longer appreciate the small joys in life.
Apparently, that is not exactly how it works, but the idea is the same. After we experience something pleasurable the first time, our brain actually releases dopamine as we crave to repeat the thing that brought us pleasure the first time. So, by avoiding pleasurable activities one is not actually reducing the amount of dopamine released in their brain, but it does help to break habits reinforced by dopamine.
I'm still waiting for the opportunity for a silent meditation retreat, but once I do I will sardonically refer to it as a "dopamine fast."