Work is seen by many as punishment for sin. It is one of the essential callings God has given to mankind. Toil — the thing that makes work exhausting and arduous — is the punishment for the sin of our first parents, Adam and Eve, a punishment we all bear.
Before the Fall, God put Adam to work. In the second chapter of Genesis, after having created Adam, the Scriptures say, "The Lord God took the man and put him in the garden of Eden to till it and keep it." God meant for Adam to work in his exalted state by maintaining the earthly paradise.
Work, however, became more of a burden after they fell from grace through sin. In the third chapter of Genesis, when Adam and Eve had just fallen into sin by listening to Satan, God came to explain the curse that is the just fruit of their sin:
Cursed is the ground because of you; in toil you shall eat of it all the days of your life; thorns and thistles it shall bring forth to you; and you shall eat the plants of the field. In the sweat of your face you shall eat bread till you return to the ground, for out of it you were taken; you are dust, and to dust you shall return.
It sounds dreadfully bleak — and it was. The earth would no longer yield to man's gentle prodding. It would only be with great effort that life's necessities could be coaxed from the earth. The fear brought about by sin even affected the animals who ran from Adam's children, making them difficult and sometimes dangerous to acquire.
Also taken from fallen mankind was infused science — a gift Adam and Eve possessed before the Fall. Now they and their children had to toil mentally with a fallen mind and soul, permanently diseased by sin, in order to acquire knowledge about the world they would have received directly from God.
Imagine: the Creator of the whole universe — of things visible and invisible — allowed Joseph to touch His hands to guide the carpenter's plane or the hammer and chisel to shape the very wood He created. He did this every day for nearly 30 years until He began His public ministry. Most likely He cleaned up the wood shavings, delivered heavy and cumbersome fabrications to St. Joseph's customers and other things unbecoming for a king, nevermind God Himself.
By engaging in work, Our Lord sanctified work and toil itself, transforming the curse that exhibited our distance from our loving God as a means of sanctification and a way to become closer to Him. He called His apostles to Him: "Follow me, and I will make you fishers of men." He called them to a higher form of labor. He spoke to people in parables about laborers and warned that those who did not toil and labor diligently were unworthy of Him.
Ultimately, He erased the old curse by commanding His children, "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you." The Lord adds He will still accompany them on their labors, "I am with you always, to the close of the age." At that time, all labor will end.
Work and toil, much like suffering, could still be a curse, but only if we would allow it. Mankind would still toil, but now they could do so for the kingdom of God — to bring life and not death to the world. Now, mankind may toil for salvation.