"Half-heartedness consists of serving God in such a way as not to offend the devil."Colossians 3:23 says that whatever I do, I am to work at it with all my heart, as working for the Lord, not for people. Yet, who am I aiming to please? Or, more likely, who am I afraid to offend (whether it be others or the devil)? Do I think I'm getting away with something when my ministry and service are done with a resentful or bitter attitude or without finishing the job well? God's kingdom and our transparency with him are what suffer the most in such circumstances, in spite of the fact that it is his kingdom we are to seek after first (Matthew 6:33) and that his greatest commandment deals with the condition and focus of our hearts (Mark 12:30). One day in eternity, I want Jesus to say he had my whole heart as I served him here.
I know your deeds, that you are neither cold nor hot. I wish you were either one or the other! So, because you are lukewarm—neither hot nor cold—I am about to spit you out of my mouth. - Jesus' words in Revelation 3:15-16