And casually thinking about your reasons why does not cut it. Instead, you must put some deep thought into whatever it is you are trying to accomplish. You must put a pen to paper and write it out. You must give yourself a clear list of "reasons why" so that you can refer to the list for motivation when you need it most.
And don't forget about using visioning as a motivational tool. Close your eyes and envision yourself taking action and experiencing your desired outcome. Incorporate all of your reasons why in your visioning session.
Build a fire in your belly. Build passion. Take action. Know your reasons why.