Hard 'n' tough...
Normally a hardening-process is followed by another heat treatment called tempering, which is also a thermal process that alters the mechanical structure of a complete workpiece.
After hardening the workpiece is refractory and therefore cannot be worked up. Tempering decreases the hardness until the desired toughness is reached.
The loss of hardness must be taken: hardness and toughness determine each other, but both of these characteristics cannot be positioned independantly.
