Wow, you've gotten a lot of great advice from people who are really good, and yet still battle with self-doubt! I have a feeling that self-doubt is simply part of the artistic territory. I was asking some friends just yesterday how it could be that I spend so much time on each piece I make and still hate them by the time I finish, because...they no longer feel spontaneous and fun! In fact, today I woke up with the specific goal of getting the spontaneity and fun back.
I really do think part of the problem is feeling pressure to make a go of art. Everyone has reasons that they might put pressure on themselves. Mine are that I am not young (not even close) and that I have some family members' voices in my head whom I have to ignore. Also, I see so much great art out there and think, "How do they work well so fast?" And being fast, they get more practice and improve, etc.
Two things keep me going: One is that when I see a really good illustration it just makes me happy and makes me want to do one myself. I don't feel that way about anything else other than doing volunteer work with people (which is a nice changeup from drawing alone all week and teaching English). The other is knowing that the only way to get better is to keep trying. For this reason every now and then I go back and look at my work from 2-3 years ago and think, "Hey, you did get better!" And that gives me the courage to go on.
So what I would say is, if at all possible just silence that voice in your head for now and give yourself time to play with as little self-judgment as possible. Don't worry about posting on social media, etc. If it helps, say, "I'm going to give myself a year." Or six months, or whatever you think you can realistically carve out in your life. Then, at the end of that time, I'm betting you will look back and see improvement, which hopefully will give you the encouragement to keep going!
P.S. Does anyone remember which SVS podcast had the four stages of becoming a professional artist? It outlined how long it will probably take for each stage and what you should concentrate on during each. It seems very relevant to this conversation.
P. P. S.
There is also a graphic that floats around on social media that shows the artistic cycle of learning and confidence. I don't know where to find it, but the point was that when you feel less confident, it's often because you are learning so much!