"Beware" is not a word that it's easy to think about Jesus saying all that much. However, it does seem like a word that we should pay attention to. In Matthew 6, Jesus warns us about living for Him for the wrong reasons. Look at Matthew 6:1-4:

“Beware of practicing your righteousness before other people in order to be seen by them, for then you will have no reward from your Father who is in heaven. Thus, when you give to the needy, sound no trumpet before you, as the hypocrites do in the synagogues and in the streets, that they may be praised by others.”

Essentially, Jesus is warning us to not miss the point of living for Him. I think it’s easy for us to start doing things for Jesus for people because of the way that WE look at people. How do you evaluate the faith of other people? How do you spot the good Christians and the bad ones? How do you evaluate a "super Christian?"