Admonish your friends in private, praise them in public.
在私底下要忠告你的朋友,在公开场合又表扬你的朋友。
would be like trying to meet a friend in London without a pre-arranged rendezvous and absurdly wandering the streets in the hope of a chance encounter.
就如同去伦敦见一位朋友,事先未约定地点,而荒唐地在街上游逛,以期待碰巧遇上一样。