We've all had moments like it: going very well, very smooth. Then something happens (or is said), and it's hard to rekindle the mood.

For me, it's a lady enquiring what they can do for me whenever I'm going down on them. I can understand some mightn't feel completely comfortable with this activity (and the fact that it tends to be ones in their early/mid 20's who say this doesn't surprise me), but it does ruin the mood.