For me personally, in my view, meth is intended to be 'intoxicating' if you will, as some have mentioned it can cause you to venture off in your mind and the desire to have fun is at maximum levels. Before I began an amphetamine regimen for my ADHD, small amounts (say 25-50 mgs would be a sufficient 'self medicating' dose) would cause me to straighten up, take a shower, make a checklist, and stay organized, no care in the world and you're in the moment. A large dose (again this is personally) would be anything greater than ~250mgs. The most I have consumed within an hour is right around a half gram. The quarter gram dose is the hot spot for disorganization, confusion, euphoria, philosophical thinking, psychedelic-like depth in thought, feeling generous, etc. After that, it's spaced out, disfunctional, blasted with euphoria and body buzz. I have little to no comedown with amphetamines, even at large doses. I experience essentially zero paranoia or delusions. I have a special ability to control that sort of thing. Meth sort of effects me like MDMA effects others. But, this was in the past. Now I don't get any sort of euphoria or lofty, positive thinking as I once did from amphetamines, which is great because they have helped me live a functional life (I am also manic depressive with intermittent psychosis, Seroquel at 600 mgs has done unbelievable things for me, certainly depression, racing thoughts, clarity, an emotion button that I keep off as much as possible [95% of the time]). Together (taken at specific times so they don't interfere with one another at the dopamine receptors) these medications (while sadly and unfortunately big pharma bullies) have done tremendous things (along with zinc, magnesium, cimetidine, and as needed klonopin, I have no problems, when once I was schizo-affective and dancing with suicide at random, along with long, hellish mood swings).
But I digress like a motherfucker, my opinion (don't take it to seriously) is this: (with lets say 25-50mgs/day)
If you can:
-find a way to manage the duration so that you sleep 6-8 hours a night
-take care of yourself, eat, drink water, brush your teeth
-pay your bills first
-take care of your children/pets if you have them (use a small enough amount so that it is not noticeable)
-take care of your affairs
-other
Basically if you can take care of your daily life/business in a fashion in which it is impossible to tell you have consumed meth it is technically possible.
If you crave more, accidently do to much, or feel 'too high', consider lowering the dose or scrap the project, take a vacation, and regain a prescription for dexedrine or vyvanse from another doctor. Try taking it as prescribed. You won't be high, but after several months, you will be amazed at what you know, what you are capable off, and how to properly use your brain! It has improved my cognition, memory, and anxiety, along with many other things.
All in all, it's a pretty tough gig, and considering smoking probably has the shortest duration (Known ppl who slept almost every night that smoked it) it is unfortunate, as second to shooting, smoking is the worst for your body (lungs especially).
Bottom line: never shoot it. I reccomend capsules. Eat a large meal and load up on vitamins (try to avoid vitamin c) and antacids, go to town. If you feel strange or psychotic-like, find a benzo or anti-psychotic from a friend and take a small dose titrating up as needed.
Regardless, be safe, and I hope you learned something. Peace and harmony. SMOKE WEED.