Reddit mentions of KISS imPRESS"ROCK IT" Short French Press-On Manicure Nails by Broadway

I imagine starting will be the hardest part. What I would do if I were you is grow them out a little bit more and then invest in some press-on nails (I recommend Impress because they're the easiest). It necessary that you get a bit more length going though otherwise the press-on's won't have anything to stick to. If you're a guy and/or you don't normally like feminine nail styles, you can get nude colors and clip them so they're not long and so the decorative/white parts aren't showing.

If I were you, I would get quite a few packs. A dozen or so you have plenty of nails. This will cost a bit of money, this method has worked for me when nothing else has though. For $100+ it was worth it... I've picked at my nails for about 21 years as well. My guess is that you'll want to pick them/ bite the press-on's off at first, so it will be helpful to be able to put a new nail on right away when you slip. But hopefully, with time, you can retrain your brain to have calm hands. For me, it also helped to see my hands look beautiful for the first time ever. It really motivated me to stop.

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Edit: Also, someone mentioned acrylic nails which isn't a bad idea either. Acrylics are almost impossible to peel off by hand (at least for the first week) whereas press-ons you could remove the same day. However, I prefer the press-ons because (a) they're cheaper so if you break and bite your nails, you can easily replace it (b) they won't destroy your nails beds (c) they're a lot more convenient.