I am quite sure I wouldn’t subscribe to the entirety of George Bernard Shaw’s worldview, but I do like this quote, particularly if the mighty purpose you recognize is a God-centered one:

This is true joy in life, the being used up for a purpose recognized by yourself as a mighty one; the being a force of nature instead of a feverish, selfish little clod of ailments and grievances complaining that the world will not devote itself to making you happy.