Actually very recently.. I saw my boyfriend of 2 years have a mental breakdown. He is normally very calm and collected. But one night we got drunk, him way more drunk than I was. And he was belligerent, threw my phone in the grass for some reason. I demanded he retrieve and shoved him in the shoulder. His reaction was to wrap his hands around my throat and strangle me for what felt like minutes but was probably several seconds. I had marks on my neck in the morning. He blacked out that night and when I told him what he had done he pretty much lost his mind for a good hour. I was genuinely afraid that he would never be the same again. He launched into very personal stories about his father's drinking problem and his father now has Alzheimer's and is not really able to communicate. He was crying and pacing hysterically talking to the me and the sky about how he just wishes he could speak to his father. He then started saying very self destructive things that I can't even bear to type. I talked him down and confessed the demons that I fight daily as well and we just cried and hugged and yeah...

TL;DR: boyfriend loses his mind after learning that the drunken night before he assaulted me.