I've had trouble over the years staying motivated to exercise, but cycling has been the exception. So long as the weather is halfway decent, I'm usually pretty eager to ride. Perhaps cycling will be your exception, too. It helps to share it with your family and friends. I have a large group of cycling buddies and some or all of us ride most weekday evenings. My BF also rides and while he's not as gung ho as I am, we definitely keep each other on track.

As others have mentioned, event rides, tours and the like are great motivators. Space them throughout the season and you'll generally have something that you're "training" for.

Having a bike that fits you well and the right gear for every season helps. So does having some tried and true routes that are easy and safe to get to. Keep your bike(s) in good working order, too, so that it's always ready to go.

Good luck and have fun.