Motivation is usually only short term. You watch a video or read a quote and for only 10 minutes afterwards will you take action towards your goal.
Discipline lasts a lifetime. If you have discipline, it will not matter how you feel; you will take action towards your goal every day and you will have an incredible probability of success.
I have written a post on discipline and motivation that you might like to read. You can find it at http://ambitionism.com/posts/discipline-is-greater-than-motivation
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"Remember though, that motivation is still a great tool to have, as it brings about the goal in the first place. When used together with solid discipline, and ambition, you are capable of anything!"