[Question] How do you deal with your players romancing your NPCs?

I'm really interested to hear some opinions and ideas on how you deal with romance between NPCs and PCs.

I have barely any issues with RPing most anything, but approaching the more intimate bits like flirting runs into some mental blocks of mine.

Any input would be appreciated!

Note: Yes, talking to players and establishing expectations, etc. is always the answer. However, I am mainly looking to hear some ideas on how I might change my approach to it, because I'd very much like to be comfortable with all that.