Do you have much of a tolerance?
Had you eaten much the hours before?
If I don't do enough of an amphetamine then it'll make me tired as fuck, but with a high heart rate. Also if I don't have any food (and low or no magnesium) in me then I won't get as much energy.
Supplementing magnesium(helps make food into energy, and amphetamine/alcohal/cocaine/coffee all empty a lot of it) and eating beforehand will help in the future. Just watch yourself and don't over use..