Well I don't know THE most interesting thing, but a new friend of mine said something to me that I found quite interesting the other day.
When you have cognitive dissonance of some form i.e. you hold two seemingly contradictory beliefs, perhaps "I like smoking" and "I don't want to smoke", it is the wrong approach to try and drown one thought out or attempt to abandon it. Instead you should assume that you are a rational being however you do not understand the thoughts you have clearly. Investigating the contradictory beliefs to a deep enough level should eventually come to a point of harmony where you can understand why you thought both of those things. I guess this is a form of mindfulness.
To use the example above, I like smoking and I want to stop smoking does work together when you realise that the want to smoke is more like a preference of colour - something relatively meaningless - and the desire to stop smoking is something with a real practical basis. Therefore by understanding the true nature of these feelings you discover that you are in one case describing something you like and in the other something you want to achieve. It is then clear you should be obviously acting upon the goal, not the instantaneous preference.