When I try to remember dreams, why do I forget?
I use to have the same problem as you I know how it is to wake up in the morning and only remember the day before. I over come this by watching a hypnosis video on YouTube, don’t worry it doesn’t have any scary images in. I used it and I remember every dream in detail and I always have at least 3-4 dreams to write in my dream journal. Its quiet amazing actually. How you can find it is by going to Ultrahypnosis’s channel and look for the video entitled remember your dreams. An example of how well it works is to read this small entry of my dream journal below.
Tuesday 6th March 2012 A door
I found myself in a vast green field will low rolling hills all around me and the wind was strong.I looked back at the direction I was first looking when I was first in the dream to find Morgan Freeman standing there I can remember all the defination on his face. He spoke in his ‘classic’ accent and said the secrets of the world lie behind the door that is to your left. I quickly turned my head left and there was a door right there and it was just a slight bit taller than me and made of a dark wood. I walked through it and I was back at home in my bed awake, well that is what I thought. The door opened Morgan Freeman was there again. And said ‘Son the secrets of the world lie were no man can go that’s why there secret’ then he said 'Now wake up go and enjoy life while you can you don’t know when its going to end. I woke up for real this time. 
can you paste a link? 
here is the link to the video.
youtube.com/watch?v=9U2N_Wao … 43c8940VDv
Enjoy remembering your dreams.
how often do you watch it?
Well it really depends,
Now I don’t watch it that much because it has sort of planted a seed in me. But when I first found the video I watched it at least 1 night before bed every two nights. Soon you will recognize more that you don’t even need it, because it is sticking with you. Even if you don’t use it keep remembering going down the stairs to your dreams like they did in that video.
hope this helps,
You probably forget them because you put too much effort into remembering them, or because you open your eyes and start moving too early.
In my opinion, the best way to remember dreams is to lie completely still with your eyes closed, and then calmly think of whatever you can remember, then let fragments come back to you by association.
If you for example were riding a train, then ask yourself “how did I get on the train? Where was I before that?”.
Basically don’t stress yourself too much, just lie still and go through the dream in a relaxed manner.
Also try to remember more and more details every morning.