Fallen off the Wagon

I used to bite my nails for the longest time i could remember. and i didnt stop there, i picked & bit my cuticles as well. then one day i decided that i had enough of my ugly fingernails and stopped overnight. i just stopped. that was 4 years ago. but now, i have started at it again and i can't seem to stop. i don't recall having a lot of trouble quitting the first time but this time it's different and i just can't seem to stop!! please help!!