Anxiety and League

So, as if the title wasn't a big hint, I have anxiety. Severe enough (combined with my depression) that they considered putting me in a home. Anyway, because of it, I have nervous tics (similar to Tourettes, but not as severe or widespread). One of those tics is now giving me issues (it's new): I flick my mouse a teeny bit, but it's enough to throw off last hitting or landing a skillshot at times, and makes my mouse hand tired, which causes issues later on. Now, these tics aren't always around; they only show up when I'm nervous or excited (or mad, which League causes sometimes). I also just generally play worse when I get all worked up, tics or no.

The reason for making this thread was to ask a question: How can I play League without getting mad / frustrated? Probably a big part of the reason why I have nearly 4,000 games in silver too. :P