I think my biggest issue with RP/involvement is that I almost always feel very isolated.
I think that many people who have spent time with me on games might be surprised by that, since I do have a very outgoing personality and I try to utilize that in my RP. But it's not always an easy thing to do, and I think a lot of times it's kind of dismissed as easy and not valued or seen as superficial.
I find I am rarely invited by others to participate in things without having to shoehorn my way in or taking on a coordinator/arranging role, possibly because they assume that if I wanted to be part of things I'd ask OR that I have a ton of other meaningful stuff going on. As a result I try to be as inclusive as possible with stuff I do, but to be honest that also often results in non-reciprocation or being downplayed as easy-for-me because of similar assumptions. That used to burn me out pretty quick. I'm better about deciding (after yes, being hurt for a little while) to just set it aside and not take it personally (because I don't think it is usually personal). But sometimes the anxiety does still get to me. I might be able to push through it on the quicker end of the spectrum, though.
I think in regards to this I'm trying more to be more accepting and realistic in my expectations. It's very difficult to try to stuff the impulse to freak out and want to pester someone to find out if they're mad at me/think I suck/if I upset them in some way, but I have found things are a lot calmer when I don't do that. I'll walk away from the screen a bit. I have gotten better about not hitting send impulsively on an OOC communication. I have a bunch of silly 2-5 minute guided meditations on my phone that I will make myself do so that I can't give in to that impulse and make things awkward. I remind myself that it's okay to feel sad/isolated sometimes, and probably like EVERYONE even the people I assume are having a blast 100 percent of the time probably are dealing with the same shit now and then too. I have been forcing myself TO do available game methods of staff involvement and to try to stuff the feeling of guilt/like I shouldn't be bothering them when they have so many more important things/PCs/Players to attend to. Maybe they do, maybe they don't, but I can still work on and submit those things anyway. It has helped some.
I'm not sure that feeling of "of course you're not good enough/your RP sucks/ everyone thinks your characters are trite and stupid" ever will go away, because it's really NEVER about the mush or the people on it, and it's something I know I'll always struggle with in RL too. I just have been trying to apply some of the tools I paid a lot of fucking money for (therapy) in RL to mushing as well. It works a fair amount of the time.