If some days you do not feel like getting out of bed, I would accept that and work that into your schedule. Are you worried that if you do that you won't stop? I find if I recognize and accept myself and behavior it gets easier to work with. If there's nothing time sensitive happening "today"/"now" then wait until later.

The desire has to come from you and your head I think, not from outside. You say you feel better when you get up earlier/more consistently so you have to work with that and decide you want to feel better. No one else can give you discipline? It's like giving up smoking or overeating, starting an exercise program, etc. It's just a habit. Don't give it any more energy than it deserves. Anthropomorphizing the bed, if it does not work (as an "enemy" you want to get away from) should be dropped. It's just a simple decision; get up or don't. It's your decision each day, who do you want to be; what do you want to do?