Holding your temper
Grinding edged tools should be an infrequent requirement around most shops. Unless you've somehow nicked a blade or a knife, honing on a stone of some sort should be all you need to do.
BUT…when you DO have to break out the grinder, strip sander or sanding disc to bring that edge back into specs and ready it for honing, DON'T FORGET…
GRINDING CREATES HEAT
EXCESSIVE HEAT DESTROYS TEMPER
Before you start grinding…be sure you have a small pan of cool water nearby to dip your blade or knife into frequently as you grind… maintaining the temper of your steel. When the blade or knife gets warm enough to evaporate the water beads, dip again.
Failure to do so will result in the temper being drawn out of the steel… seriously inhibiting its ability to hold an edge. So, don't get caught up in the moment and start grinding before you set up your "cooling pan"…or you'll be sorry !