To temper something is to make it stronger by seeing if it will break under pressure. The finest swords were made red hot, then plunged into ice cold water, if they held together, they were incredibly strong, if there were any impurities, they shattered.

The art of moving up the middle path is the tempering of ourselves, removing impurities, as it were, and opening up to the world and life around us. The more we open up, the more there is to life, and all that goes with it.