Decentering is the idea that you are not the sum total of your thoughts and emotions, i.e. that there is someone who experiences those aspects of your personality.
I like this idea, but most of the time people are going too fast to even consider decentering before they act on a thought or impulse and/or get distracted by the next one.
Mindfulness is the practice of taking a second to slow down, separating yourself from your thoughts and emotions, and deciding how to proceed with intent.
In this way, enlightenment (or, at least, plain old mental clarity) can occur many mindful moments throughout the day.