It looks like you’re already going to have plenty to read so I’ll just get to it with what worked for me.
1) watch Forks Over Knives (I’m 6’3 and went from 240 to 180 which essentially, gave me wings)
2) switch the lead rider often (your pals love you and won’t mind letting you go first occasionally. Their hoots and praise while you ride will help distract neg thoughts)
3) watch some videos (mostly about picking the right line and where you should be looking vs where your eyes are worried that you bike will go.)
4) don’t stop road cycling (too many benefits to list that transfer over to mtb)
5) use skills areas (or start on a novice or light intermediate trail when you first arrive, it gives you a second to get loose and lets your muscles know what’s coming)
6) acknowledge fatigue (the most common reason why we eat shoots and leaves)
7) change your tag (go with badassrider1234… Even if it’s just because your bottom hurts)
Seriously though, I hope you can find the enjoyment that brought you into this wonderful sport again. It had little to do with skill but a lot to do with laughter and butterflies in your belly! I ride alone sometimes which makes me more cautious but still giggly… Btw, what other sport would have this many folks writing to keep you riding?! You found a great thing, don’t let it slip away without a fight. The fact that you want us to change your mind tells me you will. Best of luck mtb brother.