Anything worth doing is worth overdoing.

The familiar proverb says that anything worth doing is worth doing well. Here the line is twisted so that "well" becomes "too much." The idea is that when something truly matters to you, a measured, sensible portion isn't enough. Passion shows itself in going past what is necessary, and half-hearted effort betrays what you claim to care about. It fits the rock-and-roll spirit Mick Jagger is associated with, and it echoes older Romantic ideas, like William Blake's line about the road of excess leading to the palace of wisdom. The attribution to Jagger is popular but poorly documented, so it is best treated as "said to be his."

In everyday life, it can be a permission slip. Say you have always wanted to learn the guitar. Instead of strumming for ten polite minutes a week, you let yourself get a little obsessed, playing the same chorus until your fingertips hurt and inviting friends over to hear the result. Of course, the "worth" in the sentence does the quiet work of filtering: it invites excess in what enriches you, not in what harms you.