I often resolve to complete a task or project but then find my enthusiasm wane when the cold reality of the work hits. Getting things done is hard. I am a creature of habit prone to find the path of least resistance. (Mostly this works to my advantage, but not always.) I tend to give-up on the most important projects and finish the smaller less meaningful ones. But I know that if I am to make a real difference in the world I need to be able to finish the big projects along with the little ones.
If you've started something and now find yourself losing enthusiasm, I want to encourage you. Do the work. It's hard but in the end, as you're leaning back basking in the glory of an accomplishment, you'll be glad you did.