I have noticed that I am one of very few of my friends who have experienced this. My entire life I've experienced intense "deja vu", and once I began tripping in my late teen years it took on an entirely new meaning. My first shroom trip began with me immediately realizing that I had dreamed this trip all before, and thus began my journey into searching for the cause/meaning of this sensation. Almost every trip I've had (shrooms/dmt) have involved me realizing that I had experienced all of this previously in a dream state. In some situations the feeling lasts for a very long time, including full recollection of my environment. My very first dmt trip made me feel like I had taken the next step into answering my question, for as the trip began I almost comically recognized that I had dreamed this before and then brushed it off as it is pretty much an expected/unsurprising feeling now. I find that I've always responded incredibly well to psychedelics and have achieved many incredible states of mind very easily. On my second shroom trip, for example, on 2 grams I achieved full ego release, the feeling of which (complete inner peace) carried over for months. I'm still searching for the meaning of this and its potential implications, so good luck on your journey as well.
Shanti
Edit: I should note that the feeling of "deja vu" occurs all the time in my everyday life. I now don't respond to it with as much shock as I used to, but I still recognize it when it occurs.
O how they cling and wrangle, some who claim
For preacher and monk the honored name!
For, quarreling, each to his view they cling.
Such folk see only one side of a thing.