why is the old man getting nagging when he gets older?

why is the old man getting nagging when he gets older?my father is like this,he is never satisfied withanything and anyone.No matter how affectionate youshow,he just ignores and his own opinions.every timeyou think otherwise unlike his opinions,he willget angry and scolds you.He is bad-tempered whenyou don't do what he orders.he is imperialist athome.he is above 80 now,but he is obstinate.I really don't want to serve him from my heart.what should I do?comrades?please share your insights with me.thanks in advance.