Scenario for your consideration:
If I don't feel like having sex with Romeo one night, say Monday night, what happens if I spend time with another guy on Tuesday night and feel like having sex with him? Is that wrong because I said "no" to Romeo the night before?
I would go into more detail over pm, I guess. That was very vague and wasn't even something that actually happened, but I'm not comfortable going into much more detail than that in public here.
Vix for short.