I hope you understand that there will never be the 'perfect' time to have The Convo. That doesn't mean you 'wade on in' when your wife is feeling down about her dad, but you surely know that something is always going wrong in her life... that's why you aren't having sex.
I'm glad you were able to be empathetic for your wife last night... and if you so choose, you can use THAT as an opener. Or any one of the million of excuses that will come up again and again and again.
Look at it this way, HD, you have a buffet of choice. Who knew?
