The problem with writing fic when one is used to RP instead is having to write dialogue for characters whose voices you haven't studied extensively.

/squints at doc how the fuck does Haggar talk...

I know what I need her to say, but I'm having trouble getting the how to sound right, grumble grumble

Hiss the dialogue smugly under your breath and see if it's good for smug hissing, that should do it

"AF why don't you just check" Because I'm sitting in the car waiting for my sister to get here, okay!!!

i enjoy it as a bit of a palette cleansing exercise

because sometimes, when you're RPing, a character's voice can derail into a flanderised version

and re-evaluating the voice of a different character... i don't know, it feels healthy to do