When do you know its time to surrender your online game for the night?

I like to play online word games. There comes a moment when I surrender for the evening. I’ve noticed three things that tell me I should quit.
1. I start to take other players points as a personal attack to keep me from winning.
2. Words beyond 3 letters have left my head.
3. I get mad when someone won by a point for spelling the word island and I am convinced that is-land is a made up word and the game creators favor this person.

So this is just for fun. What are your cues that it is time to call it a night because you have become temporarily brain dead?