Summary: 

Jin Ling makes a grave mistake and takes out his anger and frustration on Lan Sizhui - will he ever be able to repair their relationship?

As old hurts are uncovered and made open, Jin Ling is not the only one who finds themselves seeking forgiveness for past transgressions.

Link: No Love in Moderation - TheObsoleteOne - 陈情令 | The Untamed (TV) [Archive of Our Own]

Note: This story by far is very much heart breaking. Sizhui is the darling of the Lan sect. When Jin Ling hurts him unintentionally, everyone including Lan Qiren goes fiercely protective. This explores a lot of relationships... between parents and child, between friends, between brothers and many more. In simple terms, it's a gold mine.