Benzos sometimes help, but it depends on how much, how long ago, how often, etc. I'm not sure of your situation, but someone who isn't necessarily me, slams often and slams alot of crystal meth. A lot more than what is needed to stay up for the duration of my run. Years of that have changed my brain so it doesn't have the same effect it would have in my first few years. I'd say that the # of nights in a row that I sleep, free of meth, about equals the # of days I am geeked/tweeked, whatever. About 2-3 days on, 2-5 days off., and so on, occasionally taking a 1-2 week break, but I work too, 5-7 days a week, so I rarely sleep more than 10 hours at a time even if I want to, and always eat something at least once a day while on speed, even if I don't feel like it. In other words, I don't do the typical "crash" sleeping days at a time and pigging out. I just can't sleep longer than 12hours in 24, meth or no meth.
If you're talking about short-acting AMphetamine, and not meth, well, I don't have any problems coming down off of that quickly. If you're experiencing what I think you're experiencing, I wouldn't call that "messed up". You're just high and have nothing to do. No real way to turn that off like a switch. Lord knows, I wish it could be done sometimes.
You see, depending on if it's amphetamine or methamphetamine, and depending on how it was taken, chemicals that are naturally present in the brain are released in varying amounts, and in the case of meth, are prevented from being re-absorbed (reuptake) until the dope wears off. This causes the brain to shut down certain receptors to prevent damage. (mostly serotonin and dopamine) That's usually what happens when someone is said to be "over-spun". you're not really enjoying your high, but you can't sleep either. Fortunately, it doesn't shut down most of your receptors for the brain chemical called melatonin. (the chemical that relaxes you and tells you it's sleep time) When using amphetamines, and not too frequently, actually taking more melatonin can help. (you can buy it). All you need is that message that tells your brain to sleep, to be stronger than the speed message to stay awake. Keep in mind that if you take melatonin for more than a few days in a row, or too often, the receptors for that chemical in your brain start shutting down as well, and it begins to have no effect, even if you're not on speed. Effect is restored after several days of NOT dosing with melatonin. I'd say try it. A few shots of alcohol, as already mentioned doesn't hurt either. It helps to depress the message to stay awake, and the melatonin helps to increase the strength of the messege to sleep. for occasional relief from upset stomach... oh wait. That's a different commercial.
For occasional relief from the affects of meth or amphetamines, a little meletonin, and/or a little alcohol goes a long way to tip the balance to nighty-nite time. The alcohol always has some affect on depressing the speed effects, even if you get "burned out" on meletonin.
Keep in mind, you can't expect these to work if you took amphetamines 6 hours ago, or took a potent dose of meth less than 12 hours ago. If that's the case, your brain will pretty much ignore the meletonin, benzo, or alchohol and you will only get increased toxicity. Different combos or one of these already mentioned are about the best you can do. Just try them, one at a time, one run at a time, and see what works for you. Or better yet, quit speed altogether before you end up like me. You don't know what "messed up" is yet. Stop before you find out, and can't quit.