i first started 'day-dreaming' when i still had OCD thoughts,, manic episodes, etc. where my mind would not sit still. i began meditating and realized that this was an actual 'uncontrollable phenomena. then i decided that if i had to have thoughts, i should at least get something out of it.

i began imagining i was building houses; i would go into great detail about digging the foundations, laying the piping, etc. (in which i have a degree and some experience), right up to the landscaping and interior decorating. i was quite fond of some of those houses when they were done.

what i didn't actually understand until much later is that this type of focused day-dreaming is very much like meditation, which is a way of focusing the mind and gaining control over one's thoughts. well, not so much 'control over' and directing them in the ways they should go. eventually, i discovered that the 'extras', or the un-directed things that arose in my day-dreams were often indicative of what i was experiencing subliminally, emotionally, or non-verbally~!

this has proven to be a great help in monitoring myself and releasing otherwise pent-up emotions and exploring old ways of thinking and new.
i actually recommend this type of intentional day-dreaming to others, few of whom seem to understand the value of 'non-judgemental viewing' of one's own thoughts~!

i hope those of you who are finding the 'daydreaming' to be intrusive, can turn it to your advantage, gaining skill in focus and mindfulness, and all the other benefits of meditation. best wishes~~
Gus