I used to bite my nails down to the quick, however when I parted company with my first wife they started growing !
The liberal application of nail varnish helped them harden and I rarely have a problem now, if I do split a nail the application of a piece of cigarette paper and superglue, filed to shape, normally does the job long emough to play a sesion or two, giving time for the nail to grow back.
I also used superglue to fill in any cuts on the finger ends or where harden skin had broken away