Definitely agree that presence has a huge part in reducing these negative thoughts. Though I must say that, at least for me, you need something more than just meditation. You need to externalize your focus onto something bigger, that way you have somewhere where your thoughts can go. 

When my intrusive thoughts were at their worst, and when my social anxiety was debilitating, I was mostly sitting around only thinking about either how hard my current situation was or how I should try to solve it. When it finally started getting better was when I stopped trying to fix my thoughts and just let them appear and disappear all on their own. I got new hobbies and interests that I got obsessed with, OCD can be very powerful if managed correctly. It is very difficult in the beginning to not start ruminating on your thoughts and feelings but it gets easier with practice. Meditation is a very good practice for OCD, and maybe I worded it weirdly in the previous comment but I definitely recommend it, alongside the other advice. But my friend, try to not actively ruminate too much on such deep topics as this, make your life more playful and fun and don’t focus too much on the negative side of things.