Life is not always rainbows and butterflies no matter how much you want it to be. There are days full of sunshine while there are the stormy days that will drain every ounce of energy in you. During these down times, doing something feels like a burden and overcoming stress feels like a hard-fought battle.
By definition, motivation is the general term for your drive to function. It can be in the form of a reward, a person, or sometimes it can be a mere thought of the after effects of your action. Reading motivational quotes is certainly a good way to find this drive among other ways.