To lead one's soul to true joy -
Think deeply and picture in your intellect and understanding the subject of Hashem's true unity.
How the Aibershter permeates all the worlds... encompasses it....it is all filled with His glory.
He is ONE alone.
Everything is nullified before Him...Etc. Etc.
613 Mitzvos were given to the Yidden -
came Chabakuk and based them all on a single one -FAITH.
For through faith alone one will come to fulfill all the 613.
That is - when your heart will rejoice and be glad with your faith in Hashem's unity, (as though this was our only Mitzvah, for we would surely fulfill it with utmost joy) then this joy will allow our soul to soar above all obstacles that keep us from fulfilling the 613...
When we have this awareness - of Hashem's true unity - it will help us overcome anything that will stand in our way of fulfilling Hashem's Will - the Mitzvos.
Very Very b'kitzur of today's Tanya.
Thank you lessons in Tanya.