From Nate's point of view when you were in a relationship you took the good with the bad and didn't give up because of an argument or a harsh word said when someone was angry. He loved Lucien with all of his heart and would never give him up easily.
Kissing him Nate would happily do forever, his hands tightened and he practically devoured Lucien's mouth. His tongue explored and duelled with his lovers and he gave himself up to the feel of it all.