Before you put on your tallit in the morning, before you open a book of Torah, before you do anything holy at all, you need one thing first. Fear.
Not terror. Not dread. Rabbi Schneur Zalman of Liadi describes something more precise: the innate refusal to rebel against the King of kings that lies dormant in the heart of every Jewish person. Without awakening this fear, even love of God is not enough.
The practice he prescribes is strikingly concrete. Before performing any commandment, pause. Contemplate that the Ein Sof (אין סוף), the Infinite One, fills all worlds and encompasses all worlds. "Do I not fill heaven and earth?" God asks through the prophet (Jeremiah 23:24). And yet this God who fills everything has chosen to bestow His kingship upon you, personally. As the Mishnah (the earliest code of rabbinic law) teaches, every person must say, "For my sake was the world created" (Sanhedrin 4:5).
Now hold both truths at once. God stands over you. The whole world is full of His glory (Isaiah 6:3). He searches your heart and mind (Jeremiah 11:20) to see if you are serving Him properly. You are standing before the King.
The Tanya then reveals what this fear accomplishes when directed toward specific commandments. When you put on tefillin (leather phylacteries worn during prayer) with this awareness, you are not just strapping leather to your arm. The divine wisdom and understanding of your soul are being absorbed into the wisdom and understanding of the Ein Sof that is clothed in those parchment scrolls. Your mind merges with the Infinite Mind.
Fear of God is not the opposite of intimacy with God. It is the gateway. Without it, the door to every other spiritual experience remains shut. As the Tanya puts it: fear is the root and core of all divine service, the foundation upon which everything else is built.