What does it mean to become a conscious thinker?

For me being a conscious thinker means that I am aware of my thoughts and the effect they have on me. It means that I am in control of my thoughts; not the other way around. When an undesirable thought comes into my mind I simply recognize it, and replace it with a desirable thought. This takes practice, do you think you can do it too? If you don't please explain why. Remember that limitations are self imposed.