A number of years ago I heard Rabbi Mordechai Becher speak. He was explaining that while we know the reasons for some of the commandments, the reasons themselves should not be the motivation for fulfilling the mitzvah.
"We aren't supposed to eat the gid ha'nasheh, right?" he said. "Why? Because Yaakov Avinu wrestled with the malach and his sciatic nerve was damaged. But that is not the reason why I don't the gid ha'nasheh. I don't eat the gid ha'nasheh because Hashem said not to eat the gid ha'nasheh."
I thought of this shiur when I read the article "The Secret to Effective Motivation" by
Our study suggests that efforts should be made to structure activities so that instrumental consequences do not become motives. Helping people focus on the meaning and impact of their work, rather than on, say, the financial returns it will bring, may be the best way to improve not only the quality of their work but also — counterintuitive though it may seem — their financial success.