People have weird reactions. If a guy discovers his girlfriend is sleeping with someone else, he will be angry at the other guy. Why? The 'other guy' had no rel

People have weird reactions. If a guy discovers his girlfriend is sleeping with someone else, he will be angry at the other guy. Why? The 'other guy' had no relation with him, he simply met a nice girl and wanted to have a good time. The girl was in a relation with him; he should be angry at her! When I enter a restaurant, I see a price on the menu and this is what I intend to pay. When I order the food, this is my agreement with the restaurant: pay what is asked. The server might be angry at me for not giving any tip, but as with the previous example, I have nothing to do with any contract the restaurant owner and the server might have. He accepted to work for a given salary. I might give a little extra if there's a parade for me or something, but not for just doing your job.