Maybe the distinction that's being missed is "need".

If I enjoy doing things for others that add to their happiness, and they enjoy having me do them, we've probably got a pretty healthy situation going on. Especially if it's a two way street.

However, if I need to do things to make them happy... if I am attached to the idea that I can control how other people feel, and if they need someone else to make them happy, and they make other people responsible for their feelings, we probably have an unhealthy, co-dependency situation.