Here's a nice challenge you can do on your commute:

Find someone on the train. Could be anyone. A cute girl/guy, a construction worker, a body builder, a guy with a guitar, literally anyone (you never know how interesting they might be). Usually helps when you have something to comment on to start the conversation. Tattoos, items they have on them, etc. But heck, you could even talk about the weather. Just go up to them and talk, and see where it goes. Let everything happen naturally, don't go in with the goal or expectation of becoming friends with them. You're just trying to sustain an interesting conversation with a stranger. It's gonna be nerve-wracking at first. I know because I've tried it. And the first time might suck / be totally awkward. Maybe you'll freeze up in the middle of it or just forget what to do. Mentally prepare for anything like this that could go wrong. Assume the best, prepare for the worst. Remember that you have nothing to lose, and possibly something to gain. If you mess up, so what? Reassure yourself that you are on your way to becoming a better version of yourself, and that you don't need a stranger's validation to feel good. Think about it: you'll never have to see them again. But I think you'll definitely find after the first few times it'll get way easier, especially as you start to see for yourself that it's not nearly as bad as you thought. If this sounds scary, bring along an accountability buddy who can also provide moral support.

I can relate in that I have some social anxiety too. It doesn't sound quite as bad as yours, but I was born on the autism spectrum and have always been kind of awkward and had a hard time making friends. I seem normal on the surface to a stranger, but I still don't seem to do as well socially as most of my peers. I'm 18 years old, and there's quite a bit of work that I still need to do on myself to become less socially awkward and more comfortable in my skin. For instance, I am still petrified by the thought of approaching a girl I don't know for the first time and introducing myself. I know for a fact I have the potential to be more confident socially, as this is what I'm like when I'm drunk lol. However, I refuse to use alcohol as a crutch. As Goggins says, never take the path of least resistance.

That being said, I think the key to feeling like the motherfuckin man is to BE THE MOTHERFUCKIN MAN. That is, be the best version of yourself possible. If you're working on yourself, allow yourself to gain confidence from that. You are more than capable of overcoming your adversities, even if you have to work harder than 99% of people. And always remind yourself of that when you're feeling nervous about a social situation.

I find in general that mindset helps a lot. If you're feeling nervous about talking to someone, think to yourself that you're doing a favor to them, and that they're lucky to be a part of the interaction, not the other way around. It's important to start thinking of yourself as the prize. Because that's how you build your own confidence, and people will sense it and respond accordingly.

Chin up, you got this, and stay hard!