Anything that directly threatens the stability of my family.
If a chick that I'd normally eye-fuck grabs my balls, tells me I'm the sexiest man she'd ever seen, and wants to go to my house immediately - and I found myself considering the logistics of whether or not I'd get caught, that'd do it.
If, however, I'm in the same situation and feel flattered, but say, "No thanks," easily - I'd continue.
If a chick that I'd normally eye-fuck grabs my balls, tells me I'm the sexiest man she'd ever seen, and wants to go to my house immediately - and I found myself considering the logistics of whether or not I'd get caught, that'd do it.
If, however, I'm in the same situation and feel flattered, but say, "No thanks," easily - I'd continue.