"the more you take the better it gets" is horrible and deceiving advice if you ask me, or any veteran speed user, the more you take, you very soon reach a point where you are adding unwanted side effects and PNS stimulation and taking more will only make the negative aspects come alive, especially psychosis, a result commonly induced by ignoring normal sleep hygiene.
Also, just kinda on the subject, Im pretty sure that the "if you have ADD/ADHD, then you react in _____ way to amphetamines, but if you DON'T have ADD/ADHD, you experience _____, because you don't have ADD/ADHD", all those generalized blanket statements are pretty inaccurate, and often are highly subjective, I mean for example, prove your point with a peer reviewed study, although how they objectively define "thinking properly" is probably the first indicator that objectivity is not easily attained meaning subjectivity can pollute the study/research.
I dunno, I just think that it's kind of disrespectful and incorrect to suggest that those with ADHD do not think 'properly' until they take amphetamines, and the debate about amphetamines making an ADHD person "normal" but a non-ADHD person abusing amphetamines will result in desired intoxication it's a blanket statement that can't be said universally.
Because regardless of diagnosis, people with and without ADHD, all will react to amphetamines as the human body is built to. Sure, some people without ADHD abusing amphetamines might feel more tweaked out vs someone with the ADHD chemical imbalances, but I've seen people who do have ADD or ADHD and their reactions to amphetamines/methamphetamines, and I've seen it result in those with ADHD being even MORE sensitive to tweaking harder at lower doses for longer periods of time, so basically any abuse of amphetamines will cause chemical imbalances of it's own causing changes independent from and regardless of the presence of other pre-existing chemical imbalances from ADHD or other mental illnesses which are results of chemical imbalance, and of course, poly drug abuse, all playing a factor here.