Being mindful is the practice of maintaining a nonjudgmental state of complete awareness of one’s thoughts, emotions, or experiences on a moment-to-moment basis. 

Having this awareness of thoughts means also, to not get involved with them. 

To be able to become the creator of your reality and therefore the master of your thoughts, you have to detach from them to then see what you would like to change.

The realization that you are not your thoughts is the first step to be more mindful.