I'm thinking, maybe the trick is to pick an exercise that can be easily decomposed into steps, each of them requires very little time and energy. For example,

I'm thinking, maybe the trick is to pick an exercise that can be easily decomposed into steps, each of them requires very little time and energy. For example, translating one assembly to another with the same architecture might fit the description because most of the time you are just doing "translation". Of course I'm not an assembly professional so I might be underestimating the difficulty here. Another good example is carpentry. As long as you finish step X you can leave it there. There is no need to burn candles to finish all steps at once. A bad example is algorithm design. Unless it's second nature to you, it's really difficult to decompose it into steps (because maybe they are wrong steps), and even if you can, picking up from where you left off last night might actually be more difficult than starting over from the beginning.