A while back I listened to a BJJ video which really made me think about competition jitters. This is something everyone gets. Some deal with this fairly well and some don't. I think it is good to be laid back and not be too hard on our selves and just accept being uncomfortable in these situations. Becoming a better athlete is a process and there are things in this process that we can't short cut. We have to compete and learn how to ok with being uncomfortable. If you do this long enough, it does become much easier. One cool thing I learned from an awesome podcast is how it important it is to become more appreciative for being able to compete. Many people get injured or have things that come up that prevented them from competing. There are also some that just can't get around their nerves and some just can't afford to compete financially. If you are at the tournament and you are getting nervous it can be good to shift your attention and attitude to be more appreciative for being able to be there and be in good health to compete. This is something small that goes a long way and I have recommend fellow athletes and they used this mindset with success. I have met some of the greatest athletes in combat sports and I came to find out some some of these great athletes get super nervous, especially the night before competitions. I think being a nervous keeps us sharp and it is a good thing as long as we do not let it take control. I see many athletes lose just because the are not mentally prepared.
Another thing I found is that the more prepared you are, the more likely relaxed you will be. I am huge on strength and conditioning for this reason. I could not help but to notice that many athletes are in good shape deal with the jitters much better and don't freak out as much. This can be due to the boost of confidence from being in shape and I think it is due to the fact that going through grueling sessions make you tougher as an athlete. Athletes that are in shape are basically have higher resistance to physically stressors such as exercise and I find that they can also handle mental stress much better.
I use various breathing techniques to relax and focus and you gotta find out what works for you and stick with it. Russians also have found that positive imaginary can be super beneficial to stay focused prior to events.