People depending on each other when necessary is not the normal definition of "co-dependence." Co-dependence in clinical terms means two people who are emotionally fused . . . people who depend on each other for their individual senses of self.
Choosing to depend on someone when you want to do something you can't do (or do as well) alone is healthy. Depending on someone because you don't know who you are without their constant support and reflected self drains both of you and is unsustainable. That's co-dependence.
