Nietzsche and Eternal Return

I enjoyed learning about the concept of eternal return and "amor fati." In order to be happy with eternal return, you must accept and love your fate. I think its an interesting but true concept. If you are miserable in your life and want it to end, you would obviously be distraught when you found out that life is cyclical and will basically never end. Eternal return is a concept for happy people, not depressed people. That makes me wonder why Nietzsche came up with it. For what we've learned so far, he seemed to be a friendless and sickly. Why would he come up with the concept of eternal return if his life was miserable? Perhaps maybe he wasn't depressed, but it seems like no one would want to relive the kind of life he had. It is interesting to me that a person like Nietzsche would come up with concepts of eternal return and amor fati.