I've heard many say if it isn't fun anymore they will quit. Let's face it, there will be plenty of times it won't be fun. Esp when you are slogging your way through ankle deep wet sloppy slush with wind belting you at 50 mph. But plenty of times it will be the best experience of your life. And that's what you hold on to. And if you get a bad day, you will have a good day. But you will get days you want to quit. Those are the days that if you can keep going, despite the urge to bag it, all the way to the big K, you will have conquered the mental challenge.