eat, drink, have a nap, i find anxiety is worse if I give myself too much room to think as it's winding down so distractions can help, but sometimes having a nap before the meds wear off does an excellent job as well

practice breathing meditation on a daily basis, time it so that you start your practice before the anxiety comes in, that way as your reaching that stage you're already relaxed

make sure to put the effort in to achieve something, small or big, every day (find that being completely unproductive all day usually leads to me getting down on myself about it)

drink some chamomile tea, it seems to help ease anxiety for me a little bit without being particularly mind-altering,

avoid using other /drugs/ to deal with the anxiety if you can, sure a bit of weed or a bit of alcohol might help alleviate it but as it's usually when the meds are wearing off, it's easy to fall into low impulse-control territory and potentially abuse either, that being said occasionally if it's too bad i'll have a glass of wine. Used to smoke a lot of weed but these days I honestly can't stand the stuff so my opinion on that might be a bit biased, I just don't feel it's good for my over all head space and often feels like it sets me back more than it does me any good. Others may be different, but last time I tried it while in that anxiety/coming down from meds phase it threw me into extreme anxiety from a single hit, borderline panic attack, which makes sense if you consider it's somewhat psychedelic, so personally I just don't even risk it

also if you're at all drinking a lot of caffeine throughout the day, cut it down, it tends to make the anxiety worse. if not disregard this

Basically all you can really do is give your mind a bit of a rest, avoid realms of thought that can lead you into anxious mind states by engaging in something that will either calm or distract your mind prior to that sort of 'sensitive rebound' state coming on-

the way I've learned to perceive it is that it's basically like a temporary state in which I go from the functional state of mind to having my adhd symptoms come back in quite strongly, when it's a rapid shift and I haven't prepared for it, I don't really know where it's going to take me, and even though you know it's coming, if you let it catch you by surprise, it can very easily make you anxious about a lot of things, regardless of what medication you take

It might have been worse on concerta for instance because of the longer duration than adderall, being 'on' for a greater duration can wear you out more mentally for instance, personally I find with concerta the wearing off is more gradual and I get less anxiety in rebound than with instant release medication, but I definitely feel more tired and run down by the end of the day than I did with instant release