What you should do is do not go to these concerns rather than your band members that he wanted to leave the band because it is his reason, but you don't do it, you need a good peach finally enough.
What you should do Do not worry rather pleased with the members of your band. He had to leave the band because it was his reasoning. You do not discourage You just do your best, it's enough.
What you should do is Don't worry, rather pleased with the band members. He had to quit the band because it's his. But you do not be discouraged. You just do it best is enough!