Without breathing all the other stuff is practically useless. That choke, that sweep, that armbar- you’ll need to do them quickly (and more often than not sloppily) if you don’t allow yourself to breathe.
I’m fairly sure I’ve mentioned this before, but I’m talking about it again, because breathing really is just that essential. I had the same trouble when starting jiu jitsu: I would inhale and hold my breath when rolling, which is a really great way to tire yourself out before you even get started. Our instructor at the time advised me to force the breath out, because eventually I would have to breathe back in. And he was right: still to this day sometimes I’ll take a moment and make sure to breathe out when I feel like I’m getting too anxious and I feel too tense while rolling. It’s one of the most important things we need, and yet one of the functions of our body we take for granted the most. Learn to breathe in preparation for a tournament, so it’s one less thing you have to worry about when you are freaking out about competing (especially when you are a lower rank).
Learn to breathe deeply, both to calm yourself and to better your jiu jitsu. Because really, learning to breathe during those situations will help you and your game.