Let nothing be done through selfish ambition or conceit. (Philippians 2:3)

Don't we all want that pat on the back when we do something special? I think it's OK to respond with a gracious "thank you" when you have done something for someone, but we need to make sure that our motives behind the action were not for the reward of that pat on the back, but simply done for the benefit of the receiver. Most importantly, we need to forward the "thank you" to the Lord, who enabled us to do the action in the first place for His glory, and His glory alone.