Answer 1 : Sometimes the truth may not be what you expect. The truth can hurt. Most truthful words are spoken hurtfully." Let's make most words positive!

Answer 2 : "Many a true word is spoken in jest" means the truth is often found in comic utterances. The saying originated in Shakespeare's King Lear.

But in modern British English usage it is often a retortwhen some sulcastic comment you have just made to them implying you think what you have said is silly is really the truth, their retort perhaps intended to be hurtful or embarrassing to you, or it is more often just good natured banter between two individuals.