You probably think the majority of your crabbiness is caused by the idiots and sociopaths in your life plus your inexplicable bad luck on any given day. Based on a lifetime of observation, my best estimate is that 80 percent of your mood is based on how your body feels and only 20 percent is based on your genes and your circumstances, particularly your health.
Scott Adams, How to Fail at Almost Everything and Still Win Big: Kind of the Story of My Life