Basically, to control anger is to first control & calm your mind. If your mind remains in a state of calm then no negative emotions can arouse in it.
Below verse from Bhagavad Gita explains why we should avoid anger
Bhagavad Gita Chapter 16
TEXT 4
dambho darpo 'bhimanas ca
krodhah parusyam eva ca
ajnanam cabhijatasya
partha sampadam asurim
krodhah parusyam eva ca
ajnanam cabhijatasya
partha sampadam asurim
SYNONYMS
dambhah--pride; darpah--arrogance; abhimanah--conceit; ca--and;krodhah--anger; parusyam--harshness; eva--certainly; ca--and;ajnanam--ignorance; ca--and; abhijatasya--one who is born of; partha--O son of Prtha; sampadam--nature; asurim--demoniac.
TRANSLATION
Arrogance, pride, anger, conceit, harshness and ignorance - these qualities belong to those of demoniac nature, O son of Prtha.
Let's try to avoid anger & let's not hurt our near & dear one's. Krishna does not approve of it.
