One day I think it's the greatest idea ever that I'm working on. The next day I think it's the worst that I've ever worked on - and I swing between that a lot. Some days I'm very happy with what I'm doing, and the next day I am desperate - it's not working out!
I don't think you can replaces great themes. But I think people do want to hear fresh arrangements of them. They don't want to hear them played the same way all the time.
I often think that a slightly exposed shoulder emerging from a long satin nightgown packs more sex than two naked bodies in bed.