3 ideas
Effort is not linear with results: spreading energy across many activities yields shallow progress everywhere, while concentrating it on the few that matter produces disproportionate impact. The essentialist deliberately trades breadth for depth, rejecting the default assumption that doing more is inherently better.
When evaluating an option, score it against your single most important criterion from 0 to 100; if it scores below 90, reject it entirely and treat it as a zero. This forces binary clarity and prevents weak 'pretty good' options from crowding out the rare excellent ones.
Saying no to a request is a separate act from rejecting the person, and declining one thing is implicitly choosing something else more important. Because the social cost of refusal is short-term while the cost of overcommitment compounds, deliberately disappointing people in the moment protects your capacity to do meaningful work.