Well, try this if you can't go to weekly tournaments and you want to rid yourself of this habit:
Find something that you can do and focus on while playing, like music for example. Your performance will suffer because the game isn't your focus, but, over time, the music will kinda meld with the gameplay and you'll be back to normal. Now, go to a tournament and play while listening to music after you've trained yourself. If you get nervous, focus on the music. You'll lose sometimes, ya, cause your focus shifted again. Over a period of time, you'll meld play and music during a tournament.
After this, start playing without music. Non-tournament matches without music. Get used to it again. Once you're comfortable, start doing tournament matches without music. You'll find that you're a lot more at ease because, gameplay wise, you calmed down and just did your thing in the match. Only difference is that your relaxation/focus technique isn't in play anymore. That doesn't matter because, in the process of learning to play with it and calm yourself with it, you also taught yourself to calm yourself without it.