Reason to be very mad....?

I completely understand, I was in a very similar situation where I went to a party with his work friends and he and everyone else got drunk, and my fiance wouldn't leave. I just left him there. I was so pissed. I think your fiance should have been more considerate to you. He knew you had to work the next morning and you both agreed to leave by a certain time. I think you have the right to be mad given the situation. He wont see it as him being inconsiderate because he was just having a good time and was drunk