Too often, when confronted with a problem, I talk myself out of doing something because I know I can't do everything that is needed. A case in point: a family in our ward (congregation) was going through an extremely difficult time. I couldn't solve the problems they faced, couldn't really do anything that was going to be meaningful, so I did nothing.
That was more than wrong; it was selfish and weak.
When I realized that I could have made a difference, however small, in their lives, I resolved not to stand back and wring my hands. Instead, I offered what help I could. What if each of us, even knowing that we can't do everything, did something? What a beautiful world we could build.
This I know for sure: I will never be able to do everything, but I can do something.