Just as with the mitzva of tefillin for example, there is a designated place for them on the head and arm, and one feels the weight of the head-tefilla and the tightness of the hand-tefilla, so too with the mitzvot of ahava and yira, love and fear (awe) of G-d. As Rambam writes, in Yesodei Hatorah 2:1: It is a commandment to love and fear the revered and awesome G-d, as it is said, "Love Hashem your G-d", and "You shall fear Hashem your G-d."

Now the degree of fulfillment of these mitzvot is that there be a bodily sensation, that the very flesh of the heart actually feel (the love or the fear); just as, for example, when one meets a truly devoted friend. Not only does he feel good and forget all his troubles, he even enjoys a newly-awakened inner liveliness and optimism - all stemming from his cheerful mood.

So, too, with (the opposite emotion of) fear (of G-d); he is seized by a great dread and fright, for at that moment he recalls whatever was undesirable in his thoughts, words and deeds. His heart feels a palpable pain from his dread of punishment, his fear of Heaven. At times he may experience yirat boshet, an overwhelming shame,1 or yirat harom'mut, awe of G-d's transcendent majesty.2