We, the doers, like doing meaningful stuff. Whenever there is an opportunity, we take it.
Unfortunately, it's easy to spread oneself too thin. And it's not just about commitment and time. I wrote about that multiple times already. It's also about emotions, relationships, thoughts.
Think of the literal meaning of spreading something thin; like butter on a sandwich. The thinner you spread it, the less will be in each place. That's exactly how you'll end up; there will be very little of you.
It's better to do less. Say "no". Be fully wherever you are. Miss out on exciting commitments, hangouts with friends, learning opportunities. Do things, but do them well.
Once you know your capacities, make sure stay within them.