One way I've managed to get past it is thinking how politely listening to them is wasting their time - time they need to make a real sale instead of me stringin

One way I've managed to get past it is thinking how politely listening to them is wasting their time - time they need to make a real sale instead of me stringing them along. And for the ones who push past that, well, annoying/ignoring the intentions of person you're selling to is sort of a jerk thing to do, so that mitigates the guilt a bit.