Trigger warning: self harm

Not sure if this is important to mention or not, but I’ve been diagnosed with generalised anxiety disorder, social anxiety disorder, and and body dysmorphic disorder.
I’m currently doing a course in business administration and for that, we need a to learn typing and I’m having to test how many words a minute I can type and with what accuracy. Except it’s driving me mental, every time I make a mistake, it really stresses me out, and after I make a few mistakes and start crying and want to throw my laptop across the room. And then I cut myself because it feels like the only way to get my frustrations out. Does anyone have any advice on how to stop myself from reacting so severely to this?