Why do I do it?

Why is the urge to not accept good so strong? Silly little example, but so indicative of what I do all the time... last night as I got into bed it was like laying inside a cloud. The sheets were soft and the bed and pillow were perfectly supportive. And yet the urge to roll over onto my other side was so strong I could hardly resist.  Why? When I was perfectly positioned and incredibly comfortable? Why couldn't I just fall asleep in such bliss? Why did I feel the need to ruin it? Such self-sabotage is a very small thing, but I know I do it on a larger scale all the time. Why is so hard for some of us to believe that we really can have good?