G‑d has not given you a heart to know… until this day (29:3)
The chassid Rabbi Yaakov Mordechai was a lifelong oved, one who devotes himself to the service of his Creator by perfecting his character and behavior and striving to attain a true love and awe of the Almighty through meditation and prayer. For decades, he deprived himself of all physical comforts in order to refine his nature. Before his passing, however, he expressed regret at having weakened his body with such an unrelenting regimen. Perhaps, had he not been so hard on himself, he would have lived to observe even one more mitzvah. "Thirty years to sleep on a bench!" he said. "To put on tefillin one more time is far more valuable than to sleep on a bench for thirty years!"
Later, chassidim said: "True. But to appreciate the value of tefillin as Rabbi Yaakov Mordechai did, one must first sleep on a bench for thirty years…"
So, what is better - to perform one more mitzvah (even) without full appreciation of it, or gain full appreciation at the cost of losing the possibility to actually do it?
The Lubavitcher Rebbe emphasized many times that "action is the main thing". While it is true that the appreciation and passion for a mitzvah elevates it, at the end of the day, nothing trumps the simple idea of fulfilling a command of Hashem. The later Chassidim were not attempting to say that sleeping on a bench for thirty years is a good idea. They were just pointing out that it was not an entirely wasted endeavor.
Not an ENTIRELY wasted endeavor. Just sacrificing the ability to do the "main thing" for the sake of appreciation that may or may not come. Exchanging a dollar for a cent.
I'm pretty sure that not everyone who slept on wooden benches for 30 years gained such passion and appreciation.