mhhhhhh this is quite the hard question - took me quite a while to think about it so my answer might sound incomplete - im sorry :(

for there to be angst, i feel one must know the central emotional conflict of their story. what do each characters personalities and behaviours effect the conflict? are they different or are they the same? is that a good thing? or if its just one person - what are they battling with mentally?

for example, in exchaning heart, the main emotional conflict was that Soobin fell in love too late and having to reconcile with losing that part of himself. Hanahaki is a pretty straight forward trope, but its implementation was used to give greater impact to the main conflict. There is LITERALLY no hope for Soobin's feelings to be reciprocated, but he still struggles to give up something so precious to him, so central to who he was.

since i usually use third pov but just for one character, i usually like to use their mental turmoil to bleed into the real world. like, what we experience really depends on out emotions and this will also effect what we notice and dont notice. so, when writing, emotional states will dictate how the environment is described.

i also like to sprinkle in some irony, because if you think about it, comedies and tradgies are the same, its the matter of tone that differenciates it. why do you think shakespear was so good at it? a situation that makes you laugh in a normal situation can turn sour quickly with the wrong emotions. miscommunication, misunderstandings, missed timing.

i hope this helps? trying to write down my messy thoughts is difficult so i hope this makes sense! you can always dm me <3