Well, maybe enjoyable habits don't GIVE us energy, but a recent study indicates that people who enjoyed a task (habit) have more energy to complete the next task, than those who didn't enjoy the first task (and just slogged through it.)
http://www.huffingtonpost.com/max-ogles/the-1-reason-good-habits-dont-last_b_5709885.html
How can you define your new habit in a way that is enjoyable? Can you reframe it? Is there a version of it that would be more enjoyable?