Plenty of times I really didn't want to go out and ride, even on a nice sunny day. I've had that feeling even after I've changed into my cycling kit and pull a bike out of the bike cave. But I always tell myself just start the ride and if after 10 minutes I'm still in the mood to not ride just turn around and go home. It works for me and I've never turned around and went home, and have had some of my best rides when I did this.