Being angry instantly—or being overly nice—is a red flag. There's no real reason for him to leave, so he has to create one. New activities that he goes to all the time, but then never mentions when he returns is a glaring example. If he were going, he would most likely share something about it with you. The most common statements: "I need time to think. Gonna take a walk." "I need time just to be alone/be me." "I have work to do." While these are logical excuses, they are usually too often, without a reason, or completely out of his norm.