The general rule of thumb for raw intelligence probably applies, you can damage it with unwise actions (like eating lead paint or taking up boxing), but there aren't really any good ways to boost it beyond its natural unimpeded baseline. Good instrumental rationality can help you look out for and avoid self-sabotaging behavior, like overworking your way into burnout.
Decreasing work-load when you feel tired - the thing you naturally want to do - is also a reliable way to avoid burnout.
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