Be on watch for one's negativity. It is important to remove attention to all negative thoughts from one's mind. When a negative thought enters the mind, and your mind is so trained, instead of indulging and identifying with the thought you immediately place your attention on something positive. Some will use this reflex to place their attention back to the "I Am" or their idea of God, others will turn their perspective on the negative idea to positive trying to see the positive aspect of what they had perceived negatively.
You deny a thing by taking your attention away from it. To drop a thing, problem or ego from consciousness you dwell upon God - God being I AM.