Consider, if you will, the two following quotes:
"Everybody wants to save the world but nobody wants to help mom with the dishes." P. J. O'Rourke
"Familiarity breeds contempt." Wiktionary
It occurs to me that the two sayings are related.
You want to do big things, to be part of something worldwide, to make sure your efforts are employed in something that will have the greatest possible impact. But those are the things that you are least likely to have a real effect on, and even if you do, the extent of your effectiveness is almost impossible to measure.
How much better would it be to concentrate your efforts on smaller goals, closer to home, where your aid is instantly recognized and immediately useful? Certainly the rewards for such things are more measurable. But you don't want to do those things, like helping mom with the dishes. You are familiar with those problems; they are contemptible for their familiarity and smallness.
It is the problems you're not familiar with that are so sexy. You may think you know a lot about your particular world-saving issue, but compared to the problems closest to you, your knowledge is infinitesmal. It is the fact that you know so little about the big problems that makes them attractive; it is so easy to conflate your desire to help with your actual ability to do so. You congratulate yourself on having the right sentiments about the most popular "big" problems, even if your actions don't have any measurable effect.
(P.S.: This is an old post I've had on file for a long time, and since it appears I will never "finish" it, I'm publishing it as-is.)