On Shabbos, I heard a dvar Torah from someone whom I know to have a decidedly anti-rationalist orientation. I'm not sure if it was reflected in his dvar Torah. He asked why the spies, who were Gedolei HaDor, would have wanted to make the Bnei Yisrael miserable at the prospect of entering the Land of Israel. His answer was that the spies saw that the Bnei Yisrael were excited about going into the land, which was a deficiency in the purity of their motives; by dampening their enthusiasm, their goal was to make the Bnei Yisrael want to enter solely l'shem Shamayim.
To back this up, the speaker told a story about how when Rav Chaim of Volozhin originally decided to open a yeshivah, he went to the Vilna Gaon, who told him not to do it. A year later he asked again, and the Gra gave him the go-ahead. He asked the Gra to explain his change, and the Gra replied that on the first occasion, he saw that Rav Chaim was excited about it; a year later, he saw that he was less excited, and so it would be l'shem Shamayim.
Now, I'm not sure exactly what the speaker meant. He might have simply meant that sometimes excitement is an inappropriate substitute for genuine good motives. For example, charity campaigns sometimes have some sort of shtick to excite people into giving, which, while better than their not giving, is still not as good as people giving out of genuine altruism. That's a fair point.
On the other hand, the speaker might have been saying something along the lines of a chassidishe maaseh that a friend told me, about a rebbe who stopped giving charity for a month. His reason was that he enjoyed giving charity; he therefore wanted to stop, and train himself to be miserly, so that when he went back to giving charity, it would be l'shem Shamayim.
Now, non-rationalists don't necessarily take such a viewpoint. However, such a viewpoint is only found with non-rationalists.
As I noted a while back, Rambam explains that all mitzvos serve either to inculcate a truth, to improve one's character, or to improve society. To be sure, we can't always figure out how the mitzvos do this - with chukkim, we are obedient to God's instructions even without understanding what they accomplish, since we can be confident that He must have good reasons - but they definitely serve to accomplish something in this world. And with many mitzvos, it's very clear what they serve to accomplish. As such, to give charity out of compassion, and thereby to feel satisfaction from fulfilling one's compassionate drive, is not any kind of deficiency in the mitzvah; it's the whole point of it. (Rambam himself was very extreme in the rationalist approach, believing that such character improvement serves only to prepare one for philosophical perfection, but a more mainstream rationalist approach would agree that identifying with the rationale for the mitzvah is in no way a deficiency.)
Netziv, on the other hand, representing a non-rationalist viewpoint, says that “...all the 'reasons' for mitzvos are only to make them appealing to the intellect... but Heaven forbid to think that they are actually the main intent of the Giver of the Torah…” According to this approach, one should ideally not emotionally identify with the "alleged" reasons for the mitzvos, since they are not the true reasons; they are only an incentive for the weak.
Like I said, I'm not sure what the speaker was saying. But, either way, there is an important point here to appreciate. To be sure, we are obligated to observe the mitzvos whether we identify with them or not. But it's certainly preferable to identify with them - and that means identifying with the sentiments of the mitzvah. As a rebbe of mine once told me: When you do a chessed, you should be happy at helping someone; not smiling only superficially, and internally being focused solely on God. That's exactly what the mitzvah is all about, for Heaven's sake.