Living your purpose is pure joy, every day, regardless of what the weather brings. It may not be all happy and glee but there is never doubt either.
How often do we start something out of obligation or necessity yet fall short of completion? Most often, this can be traced back to a lack of inspiration; not external motivation, but inspiration, which is fueled from within.
Failed New Years Resolutions are an easy example of decisions from motivation or a want. Making a life altering decision that comes to fruition, with apparent ease and grace, is an example of a resolution driven by inspiration.
You enter the "flow" and all things align within you. You no longer need that outside motivation (although it helps) to accomplish your goal. The Olympics in Rio are in full swing. These athletes would never make it to that level on motivation alone. They are driven from something deep within themselves. A level of inspiration that creates the supreme athletes they are.
If you find yourself struggling in any endeavor it may be worthy to check in on your inspiration and alignment with your true self. If your gut isn't playing full out then there may be cause for investigation. When it is not "work" to stick to your plan, you know you are in alignment and living your authentic self.