Make a list of things you really want to do in a lucid dream and read that list every day.

Also, even for things as cool as lucid dreaming, motivation doesn't really come that easily, so when you don't feel like writing in your dream journal or don't feel like RCing throughout the day, force yourself to do it. If you wait to just feel motivated, you'll end doing what I did for the past 3 and a half years. I started learning and was really excited, then after a little while my motivation faded and so did all my practices. Every so often, motivation would strike me and I would start practicing again, but then it would fade. Don't get caught in that cycle. Keep on going and you will get it!