Clutch started slipping and then stopped slipping

The clutch began to slip and seemed to be getting worse over time. So I parked it and after letting it sit for about six weeks or so I took it for a spin and the clutch is not slipping anymore. I accelerated pretty hard in 5th gear and it did not slip at all. Could something besides wear have caused it to start slipping in the first place? If it is in fact worn out is there any reason why it would stop slipping after sitting for several weeks? I've never had a worn out clutch stop slipping for any reason. What do you think? Thanks very much.
Frank