This verse is one of the most mistranslated verses in the Torah. Can the Torah command something which is not humanly possible? Unlike other religions, that have fancy slogans not meant for the real world, Judaism is based on realty.

Thus, Rav Soloveitchik explains that this is not what the Hebrew verse actually says. It is all about knowing where to place the comas. For example, I had a Grandfather that lived with us. One day at dinner I came to his door with my knife and fork in my hand and said LET'S EAT GRANDPA. He was shocked and panic stricken. Then I said, “Let's eat, Grandpa.” and he said, “Now you are talking son, what's for dinner?”

Rav Soloveitchik translates the verse as “You shall love your friend, and therefore I G-d will be with you and love you.” Ve'ahavta l'reyachah, kamochah ani Hashem. The Baal Shem Tov similarly explains that G-d acts like our shadow. Just as a shadow mimics a person's every move, so too G-d deals with every person according to his actions and behavior.

This is what King David alludes to in Psalms 121 “G-d is your Shadow”. Let us work on our behavior to become G-d's Shadow!