I've written with a lot of people who had difficulties telling me if there are problems so I find myself stopping, perhaps excessively, to OOC discover if things are going well or if I need to correct anything.
Which has more than once just given people the feeling like I'm bored with what they're doing when actually things are going well until I gave them horrific anxiety.
Bad experiences have given me the inability to just jump into an RP with a stranger without extensive talks about the RP or expectations and simultaneously the inability to want to craft a brand new character for something that may only last four posts or a couple weeks. All of which has put off numerous more casual RPers.
Hyper fixating on a story. Like, it feels bad if a story doesn't work out. I know the chances of any RP actually coming to any kind of satisfying conclusion is next to zero (all RPs, I find, end with someone getting bored and moving on to something or someone else) but it shouldn't outright ruin my day. Hell, if it's a blow with the writing partner themself I find myself going back over the discussion/argument days, weeks, or even years later poking at things in my head from different angles like I could potentially make things better now when the whole stupid thing is long over.
Naturally, I have other ones too. I remember a fun word that isn't used as much and have to watch I don't add it two or three times in the same post. Part of me wants to try to narrate my character's thoughts and feeling, but I'm starting to wonder if it wouldn't be better to try to describe the character's body language to allow people to come to their own conclusions about how they're feeling. Except in settings when telepaths and empaths are involved, of course.