During the day I can usually keep myself busy and avoid daydreaming for the most part, as long as I can keep my mood up. However I'm finding it so difficult to avoid it at night and I'm finding that I'm spending 4+ hours every night doing it. Even if I'm exhausted, I can't stop myself.
It tends to flick between the daydream itself and just being completed devastated that it isn't real, which makes it a bit of a vicious cycle.
One of the most helpful things I have found is a blog on here by a gentleman called Alan. He talks abotu tips, how to control it and I'm doing some of the things he has suggested and it is helping me a bit. Just look in the blog section.