From “Living Without Hypocrisy: Spiritual Counsels of the Holy Elders of Optina”:

No one can blame their irritability on this or that illness- it comes from pride. – St. Ambrose

I am irritable person. I have a bad temper. I’m extremely negative when you get to know me. I regularly complain about people to my wife or close friends. I love to blame my negativity on a situation at work or my stress level. Those things are not the cause of my irritability.

It is my pride that causes me to be a jerk… not my circumstances. Though my circumstances make it easier for me to be negative, ultimately it is me choosing to indulge my pride that causes me to sin with anger.