How to not be utterly spastic????

So I just had a match as Ryze mid, vs a Karma, lost lane but not too bad. The other team had a Rengar. He instagibbed everyone, since he started to get fed pretty fast since I can only assume he powerfarmed.

We lost a teamfight but I ulted to the other side of the fight where I ended up throwing spells into Karma's shield and eventually she ran away. I saw Rengar and their Jhin at low health, so I moved to the other side to kill them. I could have finished off Karma and gotten the triple.

But I was twitching and shaking really bad. For no reason. Other than the fact that I could in fact win a teamfight.

And I blew it all. That's pretty much why I suck at League, Smite, Overwatch, you name it I'm bad at it. I can't survive ganks, can't teamfight, can't enable ganks, nothing.

Because of this stupid adrenaline rush that just leaves me sitting there like "wtf just happened"

And the funny thing is I play soccer and I deal with it without even thinking. It's all natural. Only in League does this become a problem.

Can I get some help????