I picked up My Utmost for His Highest again for the first time in a long time. If you're unfamiliar, it's a daily devotional by Oswald Chambers. You can get the book at any bookstore, or check out the readings online.
Here's a quote from today's reading that had me thinking all day:
"So often we mar God's designed influence through us by our self-conscious efforts to be consistent and useful. Jesus says that there is only one way to develop spiritually, and that is by concentration on God... If you want to be of use to God, get rightly related to Jesus Christ and He will make you of use unconsciously every minute you live."