There are always many things going on in the world, good and bad. We cannot put our own lives aside until all of them are resolved, or we will have no lives of our own.
That doesn't mean you should never take the time--whether it's an hour to give blood or years working as a nurse or in the military--to address the larger problems. Rather, it means that when you aren't doing that, it is legitimate and proper to think about small joys and large, about your loved ones and the taste of a fresh orange.