"Crystal meth" is probably fine as long as you're responsible with it and take it at therapeutic doses. It's available as a prescription drug and is indicated for ADHD and obesity[1].

[1] https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/00...

You'd be surprised (if you have ADHD)

https://www.astralcodexten.com/p/know-your-amphetamines