I‘m not an expert. But from what i know, angst-writing is all about amplifying huge, heavy emotions. So, for example, you have to set it up that the girl loves the guy so much... so that when the conflict comes in, the sadness and the anger come out just as huge! You have to write angst in a way that it‘s hyper-emotional so that your readers feel the pain along with your characters. Make it an emotional rollercoaster ride. :)

You have to think about something verrrrrrrrry sad. Like, your bias will die. (Please don't be real.)
Angst is like you regret about something you've done, etc. So make your readers cry. wth lol

I don't know if I can help.