“With all your soul,” could probably be one of the most confusing phrases ever spoken and if not for the great wealth of insight Scripture gives us concerning the personhood of Christ it would be hard to grasp the nature of what He meant.
We can look to John 4:24 for further illumination on this phrase as during his discourse with the woman at the well Jesus uses another phrase, “worship in spirit and in truth.” You’ll need to (and should) visit that passage for the full context of what is being discussed there. Essentially Jesus is speaking to the theological principal that your inner self is the true self. If you could peal back the physiological composition that contrives your physical essence and see the soul inside, you would be able to look on the real you.
Loving God “with all your soul” means that you love Him with a deep authenticity that is rooted in the very nature of who/what you are as His created being. Authentic-soul-level-love surpasses the wishy-washy nature of a cultural religious phenomenon or ritual and surpasses even a lifestyle to alter the fabric of one’s very identity itself.