Why can't I remember my GOOD dreams?

[Blackjack]

I have a friend who's been writing down his dreams for years.

The idea is that you get to understand your subconcious better and eventualy you can control your own dreams. I tried it my self once and you have to be quick before your mind erases the memory from the brain. But if you do manage to write it down, you can read it about a week later and only remember a few details, if anything it all. It's extremely weird.

For the record, I have never had the "running away from someone but you can't move your legs" dream.