I would like to be motivated.

I would like to be motivated to exercise.  I am so tired right now.  I don't wish to be defined as lazy and foolish because of my lack of motivation.  What is causing this lack of motivation?  Why am I so unmotivated?  What  do I have to do to be like Nike and "just do it"?  Is that phrase realistic for me? My lack of motivation stems from the fact that I have no real set goals.  It would also stem from being bored easily and from having so many failures in my life.  I have taken the time to give up easily and that is what I have to overcome.