Why would you try methamphetamine once? Are you looking for an experience, psychedelics are the way to go!!
If you want to focus try and meditate.
Meth is one of those drugs I wish it never existed.
I`m sure that shit just opened a nice door to stimulants for you

Plus someone who tried methamphetamine and didn`t get addicted will think they can try other hard drugs and not get addicted. As a consequance you will get used to stronger highs if your not carefull.
Its a pain in the ass that you got given it. If I was in your place I would propably smoke the rest. But dude take advice from my place, trade it for some fucking bud!