I've tried a lot of things to stop biting my nails but with no success. If there's something you have tried and worked, please share your advice and good practices.
I have just almost finished dealing with this for my 5 year old son. So here is a technique that worked.
"Mavala Stop" is a clear nail coat. Believe me when I say the taste is so yucky that there is no way but to stop putting your nails into the mouth. It took my son couple of weeks to get rid of a habit that was destroying his nails and also bothering us quite a bit. The coat wears off in about 3 days, so replenish it until the habit stops or resurfaces. The customer reviews describe more and no doubt it is the number one product on Amazon for 'Nail growth'. My son's nails are growing back healthily once again. Good luck.
Biting your nails is likely be just a symptom of something else that is eating at you.
My parents have always wanted me to stop it, gave me nail coat (which were not strong enough I guess), tried punishing me, etc. - none of those worked.
20 years later I am still doing it, but at least now I know the background reason (which is not going to be fixed easily, but that's for another site).
I bit my fingernails for about 30 years. I didn't enjoy it but seemed powerless to stop. I would do it without conscious thought.
Finally, two years ago after seeing my kids play with fidget spinners I realized that if my fingers were always busy then I couldn't bite my nails subconsciously. I bought a fidget cube and for two months it was either in my hands or in my pocket.
After getting the fidget cube I never bothered my nails again. After two months I no longer needed the fidget cube and gave it to my kids.
just look at the contents of your fingernails under a microscope, the sight of it should stop you pretty fast.