bite one's tongue不只是“咬舌头”，也不是“咬舌自尽”，真实含义是“极力克制自己不冲口而出、忍住不说会给自己招惹麻烦的话”，即“忍住冲动，保持沉默”。

【例句】
In order to keep peace in your marriage, sometimes you need to bite your tongue.
为了维持婚姻平安无事，有时你要保持沉默。

When his father-in-law visits, he always has to bite his tongue.
当他的岳父来访时，他总是保持缄默，小心说话。