Is it a pleasure after all to practice in due time what one has learnt?
学而时习之,不亦说乎?《论语·学而》
Is it not a delight after all to have friend come from afar?
有朋自远方来,不亦乐乎?《论语·学而》
Do not impose upon others what you do not desire yourself.
已所不欲,勿施于人.《论语·卫灵公》