When is it time to meditate and when is it time to act?

As a Mahayana follower I keep growing my wish to help all beings. To accomplish this, I have developed the wish to become a Buddha. As I meditate and follow the teachings, I really wish to help all beings to be free from suffering and want them to be happy, and I really can feel by my own experience that I can make them happy by practicing. Although sometimes I also have the feeling I should help in other ways. Like giving them food or even doing some volunteer work to help them to be free from suffering, at least for a short period of time. When is the time to meditate, and when is the time to help others (and of course by doing this wanting them to be free from suffering)?