Here's some thoughts...Anxiety starts from within, with the ego. Anxiety robs you of the present because you are more concerned with the future. It's usually in the form of questions or what if's. What if I don't do this right etc. People know that thinking like that is bad for them but yet they continue to "go there". Don't project past the present. You have to train yourself to not do something that's bad for you.
Try making a "rule" that makes those thoughts "illegal". I think a mind over matter approach could work here. If you are doing something that is detrimental, simply identify what it is you're doing, (bad thoughts) catch it as soon as it happens, and try and substitute it with something designed to lighten yourself up. Change the tape in your head. Get the hell out of your own way, why do you insist on sabotaging yourself?. Look at it like this....this is one thing that you CAN have control over, if you decide to. Be bigger than your thoughts. Kick your thoughts ass if they are bad for you. Treat bad thoughts like a threat and kick their ass. Appoint a mental Clint Eastwood in your head whose job it is to pummel those thoughts into the dirt. Don't be a victim of your own brain, that's insane! It's your brain and you're the boss, so flex your muscle FFS!
People act a certain way, because deep down, they decide to. They think it's out of their control, but it's not. You just have to decide enough is enough and re-program yourself.