How to calm down when angry/upset?

I am angry tonight,I don't know if it is about being alone, or being bored, or feeling unwanted.I don't even have anyone in particular to be angry with.Life in general is making me angry,the unfairness of it all, the violence and cruelty.Like today the story of the little boy that fell into the gorilla compound at the zoo and the gorilla was trying to protect the little boy but all they saw was danger so they shot the gorilla.Makes me so ****ing angry!And on personal note being alone and having no one special love and care for me makes me angry too,as does the fact my narcissistic sister tried to kill me for my money....anger,angry,anger,angry,anger,angry,anger,angry,!!!!!!!!!!!!!!!!!!!!!!!!!!!!!