At any one point in time there’s an infinite number of possibilities around you. The number of possibilities to do good is infinite as well.
Sounds like a positive thing, and it is, but if you keep moving from one possibility to the next, if you are overwhelmed by their numbers, if you lose focus distracted by the closest or fanciest one over and over again, that is equivalent to not having any possibility at all.
The understanding that you are finite and can only commit to a limited number of things in the course of your lifetime is needed to make an impact.