This is a very old saying taught to me since I am very young. In case you do not understand, it means don't do things to people that you would not want to be done to you. If you don't like to be slapped, don't slap others. If you don't like to be called a bitch, don't call others bitches. If you don't want other people to sleep with your wife, don't sleep with others' wife.

I find something wrong with this saying. If I don't mind people calling me bitch, does that mean I can call others bitch? I don't mind friends take my things without asking as long as they return it in good condition. Does that mean I can take their things without asking? I don't mind friends not returning me money owed to me, does that mean I don't have return money owed to them? IF I don't mind people sleep with my wife, does it mean I can sleep with others' wife?

But he can do the same to me, I won't mind

I have heard this many a time. I used to think it's a reasonable excuse. Now I am not so sure. Especially that when the person heard this excuse, it's too late, the damage is done.

There's also a twisted version of this saying. "Do unto others what they do unto you." Revenge. He's always slow in replying my sms, I shall also delay in replying his sms. He always say mean things about me, so I don't want to see him ever again. He spread rumours about me, I also spread rumours of him. He steal my girlfriend last time, so I fool around with his this time. There's no hope for the human race.