I know there have been similar threads but I didn't think they mentioned specifically what I meant to ask...

Anyways, I woke up about a couple hours ago and I remembered myself and knew that I was sleeping, and like usual when that happens, I felt excitement that now I could control my dreams. I began to fly and open my eyes wider and try and change my speed, the size of the moon, make hills and fields, etc., but then I felt it all fading because I must've not put enough focus into my thoughts, and then I half-way woke up.

When I was half-awake, I knew that if I stayed still and imagined I was still flying, I would feel many vibrations through my body and I would be there again, but it didn't work because I felt a strange fear, like for some reason I always feel when trying to go back to my dream after half-waking up.

I am just wondering why I have trouble staying asleep after I remember myself in my dreams.