Why does it hurt the brain so much to try real hard to remember a dream?

Because it has to search our subconscious minds while we are conscious.

maybe the dream was not that important so while 75%of the brain is sleeping,20%will probly be divided to,awareness,body temp,instant wake ups and blah blah which leaves little brain space 4 a dream, also i think it gets stalled in the short term memory coloum along with,"i forgot the milk while i was at the shop" or the "dat numba was 387..'' yeah those kind of little but 4getful things,but maybe da longterm memory is in on the dreams too,its a wonder to me ,what side of the brain sleeps anyway hope dat elped you out, dunno bout da urting side of it