I was reading Steve Furtick's blog today. He said that you need to know who you are before you can properly serve. This is what popped out at me:
"Identity supersedes activity every time. Remember that next time you feel like you don’t have what it takes to do what God has called you to do. And let what you do flow from who you are."
This may be something that we know but we don't always remember. Getting burned out? Feeling unsure? Maybe you are serving beyond your identity.