I've got a real interest in the psychology of sleep in babies and toddlers. I would say that your version of gradual withdrawal is what is causing all of the sleep fighting. I would do Gradual Withdrawal, but I'm a very different way to you.
My explanation for the psychology is that your baby does not want you to leave. Knowing you are there helps baby feel secure enough to relax, knowing you are there.
Your constant trying to withdraw, leave baby, means that baby has learnt that the only means she has to stop you keaving is to stay awake. Baby knows that the moment she relaxes and stills (Never mind actually goes to sleep), you leave. And she doesn't want you to leave.
So she battles against going to sleep so that you don't leave her. She only eventually goes to sleep not because she feels secure, but because utter exhaustion means she cannot fight to keep you with her any longer.
Compare to my version of gradual withdrawal:
Stay with baby giving as much reassurance as baby needs. Don't move away from the cot in any way until baby is fully asleep.
I also add my hand on baby's chest/back so that baby can relax and close eyes and still feel that I am right there, even with eyes closed. Since eyes closing is a necessary step in going to sleep, this touch feeling has an important psychological role.
Because there was no battle to make me stay, going to sleep took 5 or 10 minutes usually. Never more than 15 minutes. It will take you a lot longer than this initially, because the trust is gone. Psychologically, baby doesn't trust that you are going to stay and comfort as much as is needed.
By 8 months I'd been gradually reducing how much reassurance was needed for several months. This doesn't mean leaving and coming back. It always means staying until fully asleep and always giving every bit of reassurance baby needs. But gradually refucibg how much reassurance baby needs.
So by 8 months I would be putting baby into the cot, stepping over to the other side of the room and leaning against the wall until baby was asleep. 5-10m it took. If baby needed any reassurance I'd go over, hand on chest/back until settled, then withdraw back when calm. Wait until asleep, then leave. By 12 months I was placing child into cot standing up, kiss nan night, leave and close the door.
Sorry for the rambling post - but you did ask.
Your actions are what are psychologically causing baby to battle going to sleep. Either:
- quickly get baby to understand you will not be there for her when she goes to sleep, so she needs to develop security in her own quickly
Or
- stay and provide the comforting presence, without the battle of "will mummy leave as soon as I go quiet?"