"Made a decision to turn our will and our lives over to the care of God as we understood Him."
Step Three is like opening of a locked door. How shall we let God into our lives? Willing ness is the key. Dependence as a means to independence. Dangers of self-sufficiency. Turning our will over to a Higher Power. Misuse of will power. Sustained and personal exertion necessary to conform to God's will.
Consequently, in Step Three we turned our will and our lives over to the care of God as we understood Him. For the time being, we who were atheist or agnostic discovered that our own group, or A.A. as a whole, would suffice as a higher power.