I keep my laptop right next to me after every trip, I write as much down as soon as i come back. Often things come back to me a few days later or after a good nights sleep. Your brain isnt used to that frequency of experience and so much crams in in such a small amount of time, it all stays in there somehow, it just needs time to bubble up to the surface. Its the same with dreaming, i learnt how to remember my dreams by keeping a notebook beside my bed, if id wake up from an amazing dream id write it down as soon as i woke up, and id find more and more would come back to me as the day went on.
Lucid dreams and astral projections are also very hard to hold in the everyday mind, our animal brains seem to be designed to filter out all the useless psychedelic information and function on a survival mode in the 3d world. We have to train ourselves to be multidimensional beings, i believe its part of our evolution to migrate up into the realms of hyperspace. I think about my trips alot it seems and the more i try to understand and remember what happened the better i get at holding it all in.