Personally, this only works for me, but I will tell you nonetheless (and also because I don't want this about me page to be quite empty even if the following that I'm about to tell you is in fact just a load of bullshit)

I have three methods on how to handle nerves, which is the following;

1. Unconscious or not think at all
In this method, I simply don't think about the play or anything, I simply focus on the play itself to the point that I don't have nerves, although You could be easily distracted so be careful (at least for me) (also I learned this from Koishi, thx koish)

2. Self deprecation
I do not recommend this method because it can impact your mood on your session. In this one, when I'm finally nervous, I simply tell myself bad or not encouraging sentences such as; "You're not good at this", "Everyone could do this, so why do you have to be so nervous", "Do you actually think this is impressive? Even 6 digits could do better than this" and many more. Again, I do not recommend this, but it's one radical way to lose your nerves while playing.

3. Play with nerve
In this one, I just let it be because I couldn't contain it, or I just want to spice up my play. It's fun playing with nerves, and it could also be considered a skill to play with them. One thing that I observed from this is that sometimes nerve can give you a speed boost at the expense of well... fucking everything up, good tool for emergency during tourney! (try playing with it, it's fun)

its broken oops