Here is where the idea can feel a little abstract, so it is worth being specific. Legacy-building is not a separate activity you schedule alongside your work and your relationships. It is woven into both; it is the quality with which you do the things you are already doing.
It is the manager who takes an extra ten minutes after a difficult meeting to check in with the person who seemed most affected by it. Not because it is in their job description. Not because anyone will notice. But because they have decided, as a daily practice, that the people in their orbit will be better for having encountered them, and that this decision does not require an audience.
It is the professional who, when they make a mistake, says so clearly and early, rather than quietly hoping it goes unnoticed. Not because admission is comfortable, but because they have built honesty into their daily operating system so thoroughly that the alternative genuinely does not occur to them as an option.
It is the leader who reads, reflects, and thinks carefully, not to appear intellectual, but because they have decided that clear thinking is a form of respect for the people who depend on their judgment. Who rests intentionally, because they understand that a depleted leader is a liability, not a hero. Who asks for feedback not as a performance of humility but as a genuine practice of self-improvement.
None of these things is grand. None of them will make the highlight reel. All of them are legacy in motion.