Work is the means by which Yoga is performed and perfected

Work is a means of life in Grihastha and Vanaprastha.  Jiva is a word that means "condition of life" or "manner of life."  A coppersmith is a tamrajiva: copper is their life.  Grain, the basis of human diet, is jivanarha.  When life ends (jivananta), it is understood that the conditions for living have ended, in the sense that a candle is extinguished when deprived of oxygen, wax fuel, or wick to carry wax to the air in fueling combustion.  Work is the means by which Yoga is performed - and perfected.