It is difficult, as I have tried it. Well, sort of -- like this:
My bed headboard is the type that has balusters (I guess you call them) at either end. It's a queen size so I can stretch my arms out to the side and still be on the mattress.
Anyway, I've tried binding myself to the bed. First I tied off my ankles to either side. Then tying one wrist to one side of the headboard. I slipped my free wrist into a loop prepared that fit snug but that I could free myself from (I practices a lot before committing to this!). There I was, spread-eagle on my bed, naked, on a hot summer evening with the AC turned off long enough so the bedroom heated up. I tied myself at dusk and laid there as the room darkened. I was resolved to remain there all night, letting my fantasies run away!!!
It was exciting, and damn hard to fall asleep! When I finally did drift off I had vivid, intense dreams that were not necessarily crux or bondage related. It was interesting waking up in that position on my back. As consciousness returned I realized I was very horny, and there was just a moment of panic until I realized I had done this to myself.
Did I say I was horny? Oh yes, very!!! I so wanted the door to be shoved open and a shadowy figure come in to furiously rape me as I lay!!!! (Well, at the least the fantasy of it.)
I managed to last until dawn. I released myself went to the bathroom to pee, then went right back to bed and curled up with my hand between my legs, savoring the sexy, tingly sensations that suffused my body. I slept for several more hours, waking very anxious and still horny....
Another time...and I hope you dear readers don't find this too disgusting...I put a plastic sheet over the mattress first. Then mattress cover and sheet. Then I could piss during the night, rather than hold my pee. Yes, nasty, isn't it?! But I wanted the sensation of being bound and helpless and needing to empty my bladder. All part of my fantasy....that I was able to actually experience.
What do those poor women bound in dungeons do, anyway?
To actually be tied to a cross on the floor of a cold, dark basement all night, and be unable to free myself until the person who put me there, comes by. Oh my, the experience of being unable to free myself would have been awesome!!! But I never trusted anyone enough to do that...