The playground of the mind is rooted in the battleground of the heart. When you sinned yesterday, it most likely began in your heart and filtered out physically through your mind and actions. Consider Adam and Eve. The sin was already done in their hearts, Adam by not watching over his bride and Eve, when she considered the possibility that God was in fact, lying.

Romans 7:24–25 [widescreen]

10 Now I Paul myself beseech you by the meekness and gentleness of Christ, who din presence am base among you, but being absent am bold toward you: But I beseech you, that I may not be bold when I am present with that confidence, wherewith I think to be bold against some, which think of us as if we walked according to the flesh. For though we walk in the flesh, we do not war after the flesh: (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;) Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ; And having in a readiness to revenge all disobedience, when your obedience is fulfilled.

The Holy Bible: King James Version, Electronic Edition of the 1900 Authorized Version. (Bellingham, WA: Logos Research Systems, Inc., 2009), 2 Co 10.