This is a topic we talk a lot about at our college. Teaching adults it is easy to slip into "friend" mode. This is a big mistake.
Students need to see you as a professional. Not above the class as on a pedistal, but as the professional instructor they are paying to learn from.
You can and should be "friendly" but not "friends." Can you think of a time that you, or another instructor fell into this trap? How did it end?