She knew from bitter experience that it would be impossible to talk it over with Julian.

【bitter】因为有过痛苦的经历，她知道这事没法和朱利安商量。

It is that teachers have learned from bitter experience how little history their pupils retain as they pass along the regular route.

教师们从痛苦的经历中了解到，当他们沿着常规路线前进时，他们的学生所记住的历史是多么的少。

I can talk with conviction about this subject of being yourself because I feel deeply about it. I know what I am talking about. I know from bitter and costly experience.

我可以自信地谈论做你自己这个话题，因为我对此深有感触。我知道我在说什么。我从痛苦而代价高昂的经历中知道。