Your success or failure as a leader is intrinsically bound with the success and failure of your team. You cannot succeed if your team fails. It is very hard to fail if your team succeeds.
As such, if you want to be a successful leader, you should do everything in your power to ensure your team is successful.
Similar things can be said about the sense of energy and purpose you get coming to work - it is heavily tied up with the sense of energy and spurpose that your team brings with them to their work.