Feeling sexual attraction to your spouse is not a sin. Concupiscence is what you'd regularly be concerned to avoid and this has to do with sensuality which is not restrained by human reason, i.e. being vicious and subordinate to your desires. But I do find this to be an interesting question nevertheless. What is the case when a spouse is deceased and the lustful thoughts don't have any real object in the world any longer? Can I get a Catholic in here please? @KingOfWhiteAmerica @PS I grasp that the marriage is technically dissolved by the death, but what to do about the sexual impulse at that point... EDIT: I am sorry for your loss, fella. That has to be absolutely gut wrenching. God give you strength to keep pushing. Hopefully some of our Catholic friends can give you some solace on this issue.