וכפי מה שמשתוקק האדם כל היום לקיים המצות כך יכול לעשותם באמת – הכנה למצוה
כן הוא בכל פרט כשעושין המצוה בשמחה נשאר כח המצוה באדם לעולם – שמחה של מצוה
When you think about it, there is a fundamental difference between doing a mitzvah and anything else we do. Actions we take are geared toward results; the actions themselves have no intrinsic value. We turn off the light because we want the room to be dark. We shlep packages to get them to their destination. We eat for health and for pleasure. The action involved is just an אמצאי, an intermediary. In fact, we would often prefer someone else do the action while still engendering the results we want. This is the underlying goal of technology in particular, more results for less work.
Mitzvahs are different. Besides for the results of the mitzvahs we do, which are way, way above the realm we reside in, there is significance to the action itself. On the contrary, from the words of the Rebbe it would appear that it is ONLY the action, the מעשה המצוה, that we can relate to. The results of our mitzvahs are too elevated to be compatible with our world, which is why שכר מצוה בהאי עלמא ליכא . They vibrate on a different frequency, one we don’t have access to (yet).
However, אנו עמלים ומקבלים שכר, we can tap into the action itself, separate and independent of what we are trying to achieve. Because in addition to the desired result, of which each mitzvah has it’s own unique goal to achieve and world to build, there is the overall goal of אמרתי ונעשית רצוני, Hashem commanded and we listened. And that has NOTHING to do with what ends up happening, but rather as to the action we took. Did we try to do God’s will? Then we have already won. Because whether or not the mitzvah ends up accomplishing its goal, indeed if it even ends up being done at all, is totally out of our hands. We don’t have a say in outcomes, only He does. We have a say in action alone. So that is where we must direct out efforts, that is where our growth comes from, and that is where the mark left on us by the mitzvahs we do lives on forever.