Before a person performs a mitzva, he should take time to contemplate the fact that God is standing over him, that God has commanded him to fulfill this commandment, and that He scrutinizes the thoughts andemotions of his heart to determine whether a person is serving Him properly.
In the past, there were hasidim who would stand with a tallit wrapped around their shoulders for hours on end contemplating these matters.
Some stayed that way for the majority of the day, because they needed to reach an understanding of certain concepts before they could put on the tallit and tefillin and begin to pray.
There was once a hasid who was asked why he always arrived late for the prayer services.
He answered, referring to the first words that a Jew recites upon awakening each morning,
“It is because of the Modeh Ani prayer.
When I wake up in the morning and recite ‘Modeh ani lefanekha,’
I am thankful before You,’ I begin to think:
Who am I?
What does ‘thankful’ mean?
What does ‘before You’ mean?
And before I know it, half the day has passed by.
Rabbi Adin Steinsaltz