First of all, I'm telling you the answer . . . joy! Yes, joy!
Now for the question. How can you tell if you are serving and leading in your strength or in God's? I know you know the answer - especially since I started this post with the answer!
Joy! If you are serving in God's strength you'll have joy . . . and it should show in everything you do. If you are serving in your strength, you will show stress, frustration, irritability, etc.
How do I know this? For one reason, because Nehemiah 8 and Psalm 28 tell us when we serve and keep our focus on God, His joy is our strength. The second reason I know this is because when I serve I experience God's joy and this joy gives me the strength I need to serve.
So, take a good look. Are you serving in God's strength or your own? Are you experiencing joy? If not, is it because you are serving in your own strength? If you say, "yes", then consider this question - why? Why would you try to do something as important at serve in the Children's Ministry at your church on your own strength? Especially when God wants to bless you, generously, with joy? Plus, whatever we do in our own strength will not last, but whatever we do in God's strength is sure to last! God does not call us to serve for it to be a burden or to bring us stress; He does it so we will experience His joy! Joy is a gift from God - serve in His strength and enjoy the joy!
And, then, when you commit to serve in God's strength, remember to show this joy, so others are able to see it . . . and want it for themselves, too.
Oh, and, by the way, joy could be your best recruiting method!