When is is it too late ?

Just thinking about when exactly is it too late to change your mind ?
Every play should have a safe word or safe sign (when gagged) so there should always be a way to say 'stop'. However part of the thrill is knowing that it is increasingly 'too late'.
I think the first obstacle is knocking on the door and entering. Once through the door it is difficult to say 'sorry, changed my mind'.
Next act would be stripping naked, as you can't really run out of the house and down the street.
Then there is the bondage/restraints..... hand cuffs ? ankle cuffs ? do they make a lot of difference ? It's not until you are moved to the furniture/contraption that I feel it is getting very close now... When the winch handle turns and you are being stretched up to the rafters ! I always feel that when on the whipping bench and I offer my wrists to be secured that this is a major point in the submission ritual. ... and then finally, the gag. To me the gag is the final stage... and in some words from long ago, 'once gagged it is too late to change your mind' .
Then of course there is the realisation that it really is 'too late'. When is this ? When the first stroke lands and you realise it hurts 100 times more than it should !