I was just wondering if some of the exercises like Yoga will help....
One thing which I found helpful was meditation. If you meditate i.e. concentrate or try focusing on your inhaling and exhaling while sitting in a relaxed posture with the spine in a vertical posture for a few minutes everyday, you might feel much more relaxed and feel slightly more focused. It also helps if you engage in vigorous physical activity like jogging, swimming and other aerobic exercises. I was also reading certain research articles which state that aerobic exercises like running/jogging can contribute to development of new neurons in the brain. So, this could possibly mean that physical activity might alleviate certain symptoms like depression which can affect an individual who has not been daydreaming for some time.
I also recommend breathing exercises like pranayama. These exercises can be done prior to engaging in meditation. Again, none of these exercises are complete solutions to the problem and there might be relapses of strong desire to start daydreaming. But it certainly helps.
I've tried all of these before, and I always end up daydreaming in the middle of it. My dreams are triggered the second I stop concentrating on something, and I have a short attention span outside of my daydreaming, so meditation and exercise have never worked for me. Hopefully they work for some of you guys.