The main problem with amphetamines is that they "desensitize" dopamine through down regulation of the receptors on the dopamine brain cells, this is essentially how tolerance works. This is not permanent, the receptors will up regulate with time, but it can take many months to a year to get close to normal. The first couple weeks or so will be the worst however, it will get much better after the 1st month of sobriety. Exercise is a great natural anti-depressant and many studies have been done on the benefit of cardio regarding recovering from amphetamine abuse. I believe 30 minutes of cardio 4 times a week will greatly speed up your recovery, if you can motivate yourself to do it. Sleep is also very important, the effects of chronic sleep deprivation are horrible and it can take a long time to start making up for lost sleep, by some estimates it takes more than a week to make up for just one night of lost sleep. I should point out that you make most of your new brain cells in your sleep, and also that exercise increases that generation of new brain cells greatly.
Exercising regularly and sleeping regularly will increase your recovery speed greatly. Best of luck to you, I hope you can get sober now before its even harder down the road.. Any questions are welcome. Feel free to PM me any time.