Thalamus: The thalamus regulates alertness and consciousness, and if you aren't getting enough sleep as you should, it'll definitely affect your behavior.
Hypothalamus: The hypothalamus helps regulate stress, and if you're stressed out, your behavior is going to be affected.
Hippocampus: The hippocampus helps out with emotions, and it should be pretty obvious that our emotions affect our behavior.
Pituitary Gland: The pituitary gland helps with our development, and if you don't develop correctly as a child, it'll most likely affect your behavior in the future.
Midbrain: The midbrain helps with audio and visual processing, and if either of those are messed up, it'll affect your behavior
Pons: The pons helps with sleep, and if you're not getting enough sleep, your behavior is going to take a hit.
Medulla: The medulla helps with involuntary responses, such as vomiting, and if your medulla is messed up, your behavior is obviously affected.
Cerebellum: The cerebellum helps with voluntary movements, and this affects your behavior.
Cerebral Cortex: The cerebral cortex helps with memory, and if you can't remember things correctly, your behavior will be impacted.
Corpus Callosum: The corpus callosum allows the two hemispheres of your brain to communicate, and if the brain can't communicate with itself, your behavior will be impacted immensely.