For badly scarred self-healing mats, it's possible to continue using them for an extended period. This doesn't mean I know how to heal the self-healing function (haven't had my thrift store mat for long enough to tell), but the one I bought had initials carved in it, blade cuts, a few puncture and twist bumps, etc, and I was able to make it smooth again. I laid it flat and sanded one damaged square at a time using the fabric-style sanding material, sanding in vertical, horizontal, diagonal, and small circular motions. After removing the scars, I sanded using water to help smooth the surface. Yes, it lightened it, yes, it removed some of the grid lines, but the thing is totally usable which is all I ask for. :-)