When you can say that you do not really need a university to achieve your goals since you are on a great trajectory- you are noticed at a city-wide, state-wide, nation-wide, or international level, you have plans and are pursuing your passion to make the world (or some corner of it) a better place; but that the college (e.g. Harvard) could accelerate your life purpose in some specific tangible way, then you can feel more assured of being accepted. This is what your real-world mentors mean when they say to expand your passions- they mean not to increase the number, but the intensity and impact. That is also what is meant by @T26E4 when s/he says:
That could be tennis or boxing (can you enhance Harvard’s team?), or it could be some other endeavor. Being a participant in a leadership conference is plain-vanilla. Continuing a relationship with an ex-physician to the president, to a former surgeon-general, or to an Ebola survivor (whom you met at said opportunity) and collaborating on an impactful initiative- that is passion in action. You have been given access to these people, how will you leverage these opportunities? How will you make your way in this world? Universities are truly looking at how you leverage the cards you are dealt. You have been dealt some winning hands. You have had the personal contact and connection. Presumably, you have the email addresses. What is it YOU will do with that raw material? Depth of a passion is much more important than multiple passions (third after grades, then test scores, of course). You can see how these opportunities are double-edged swords. Tell Harvard you went, and they now know you had opportunity- what did you do with that opportunity- that is the key question.
If you are working on, say, a nationwide smoking-cessation initiative that you started with an ex-surgeon-general, you may feel the urge to take time off from college to pursue this passion. You don’t need Harvard to take your next step, but attending Harvard may accelerate it. If you are qualified and can handle the academics, why would they then not take you?
Note, this is way overboard and not necessary to acceptance- but certainly a good target to form your ambitions as a Sophomore on how to be irresistible! It gives you a framework for the mindset that (I think) you are seeking.