Ah right awesome replies thanks.

I stopped because I was paranoid I would end up like a zombie and lose my ability to perform in employment and socially but that maybe isn't the case? lol
It isn't the case at all. I'm a regular meth user and sometimes I go on multi-day binges, and I haven't touched any for two weeks (no funds ATM), and I'm doing fine. The first few days are rough, but you recover fast. Your brain can fully recover in months.
Pretty much the majority of the withdrawal is psychological, that is, after a few nights of sleeping and eating only. However, with long-term meth use, it can be very hard to recover, at least in my experience.
Meth is more addicting than heroin because the withdrawal is so psychological. Heroin, you are dopesick and want to feel good, meth, you simply don't feel cognitively right, depression, withdrawn, but it comes-and-goes.
I'd not recommend someone just trying meth, because the experience is so incredibly easy to lead into full-blown addiction (like me). The reason? It isn't like heroin or cocaine where it really is mainly a party/relaxation drug, it really is beneficial to getting boring work done, leading to it being easy to slip into chronic usage, and then the withdrawal makes it so you can't ever quit if you have any kind of social or working life, as you need energy to do it.
Meth causes irreversible damage though?
It more leads you to levels you cannot obtain without it, and usually the damage it causes is it depletes your ability to function without it.
While you do gain tremendous boosts of confidence, energy, sociability, creative ideas, and other good stuff, depending on the experience, it also takes from you those things as much as it gave, leading to you feeling very drained for awhile, while you slowly creep back to baseline. Problem is once you are used to being up, you don't want to be down further than when you started at baseline, so chronic use becomes a problem.
The only irreversible damage I'd be concerned with is how it shifts your reality. You will not be the same person afterwards, that is for sure. I just don't know if it is psychosis or if it is like cannabis, a religious vehicle.
Either way, I'd recommend avoiding meth for the most part, or leaving it to weekends. Too easy to slip into a chronic user than be out of money and fucked for awhile (happens to me).
Still, a great drug overall if you don't mind being hooked.