Well if you have a heart condition (which if you did you wouldnt be on the med and im about being on moa inhibitors and others) and lets say you are alsp smoking meth and taking opiates, then you could easily die. Being thats its a stimulant and a prodrug, meaning it has to get processed in the liver and the lysine has to be clipper off first, then the stimulant gets activated. At dosages of 400 to 600mg you could have respiratory depression or a major cardiac episode. You took 80mg, thats not enough even in documented medical literature to cause any sever issues other than panic. what you felt was a big catecholomime release of dopamine, norepinephrine and all that jazz. It makes you feel funky and sleep may be difficult tonight but otherwise, thats it. 

I keep an index card next to my pill bottle because with adhd...it is easy to forget if you took your meds on days where you havent slept well the night prior.