Maybe it's not the best habit of mine--I have a hard time saying no and a hard time breaking character as well--but I usually keep the RP going until I'm forced to end it for OOC reasons, even if I predict beforehand it's going to end that way. I'd like to hope I don't usually waste anyone's time with this, though, as I try to keep it all as true to IC as I can. If someone wants ERP and I don't, my character will turn them down, or if for whatever reason my character refusing sex is not IC, I will go along with it but ask to fade to black. I don't really feel bad about it because, well, no one should be dead set on ERP they were never promised.
But if someone becomes abusive or all around weird OOC, I have no problems ending or retconning an RP with no hesitation.
But if someone becomes abusive or all around weird OOC, I have no problems ending or retconning an RP with no hesitation.