All existence is like a single man, and you are like a single finger of this man. If you gain power over this finger (which is your soul), you will gain mastery over all of existence, conquering and overpowering it whether it likes it or not. You will then be able to act in existence however you please, and nothing will happen therein unless you please.
If you are overpowered by this finger (which is your soul), however, then all of existence will overpower you, dominating and conquering you whether you like it or not. All of existence will do with you whatever it pleases, however it pleases.
If you gain mastery over your soul, all of existence becomes your slave; if your soul gains mastery over you, you become the slave of existence. Now mastery over the soul can only be achieved by gaining knowledge of ‘those who know through God’ (al-‘arifin bi-Llah), and by keeping their company constantly.