I've been abusing dexetrine for years. I try to come off it my whole body crashes. How do I quit taking them without crashing so hard?

Seek treatment. Tapering dose down gradually may minimize the crash but the safest method is seeing an addicitionologist (an md who specializes in addiction medicine) who can offer you a comprehensive evaluation and plan a safe and effective treatment including medications that can alleviate pain and the "crash". Don't forget quitting is the easy part. Staying off is the challenge. Go for it !
Need professional . Some people really aren't destined to be able to be entirely independent of the medication. You need a therapeutic alliance with a professional that can carefully monitor your blood levels, and work with you to avoid the abuse cycle swings. .