Brachos 8a: One who benefits from his own exertion is better than one who fears Hashem. Regarding the latter it says, "Ashrei"; regarding the former it says "Ashrecha v'Tov Lach" -- you will be happy in this world and it will be good for you in the World to Come.

Rashi: One who benefits from his own toil, he inherits two worlds (this world and the world to come).

Radak: The good is to benefit from his work, and not from others, as long as he himself can word. If you do so, people of the world will be Me'asher (approve of) you, and you will get good reward from Hashem.

Malbim: If you will exert with your hands only the amount that you will eat, i.e. you will not toil to increase wealth, only what is necessary for food, then you will be happy - happiness of the Nefesh with good of this world.