I think Vyvanse hurts my writing skills

I'm doing my prep for the LSAT and there's a writing part.

It helps me focus and with my hyperactivity a lot, I can't sit still 30 minutes even without it. However, it seems that it makes me so focus on every single word I wrote that I simply run out of time.

Don't know what to do, but I'd be happy to receive some form of advice.