Self-destructive behavior
Many peple who lack self-confidence show self-destructive behavior. They think they cannot handle the stress. Because they are not self-confident, they ask themselves questions,  in a relationship, whether the other person is truly faithful ("how can they love someone like me?"); at work or school, whether the realization of assignments and deadlines is possible ("there is no way I can complete all my work on time"). Self-destructive people usually lack healthier coping mechanisms, like asserting personal boundaries. As a result, they tend to feel that showing they are incompetent is the only way to untangle themselves from demands.