In my fantasies, I would always give myself willingly. This is why, in fantasy at least, I do not have any limits. But in reality, I do have limits and, try as I may to force myself to go past them, there is always a point at which I no longer want to go on. At that point, I may be forced to go past my limit. (Usually I end up admitting that I enjoyed it.)
It is interesting to note that in any SS&C BDSM relationship the sub does have the ultimate power, wether it is to impose (I should say request ) a limit or to make the descision not to have limits at all and be willingly forced to endure any and all of the dominant's whims