Anger and Frustration

Anger is a normal human emotion. However, a lowered tolerance for frustration and a tendency to get angry more quickly are overall results of any form of brain injury, particularly when the brain's frontal lobe is damaged.

You may be more disinhibited or have trouble controlling your emotional impulses. 

Humans ideally develop from being screaming babies with no emotional control through childhood and adolescence to being an adult who can think before expressing emotions. Our brains mature, and our brain cells are wired together to form neural pathways or structures that help us control behavior and inhibit primitive impulses. 

After brain injury, these neural pathways are shaken up and become damaged. Alongside this problem of disinhibition, involving the damaged frontal lobes, the person with a brain injury is under enormous stress in everyday life. It is incredibly frustrating to keep forgetting things, make careless errors, or be less quick-witted. This stress creates anger.