If you see a little child you can see the spark in their eyes. As we grow we keep loosing that spark. Life gets harder and keeps sucking the motivation out of us. I think motivation is the most precious thing in life and we loose it so easily without even being fully aware of it. As I grew up the most difficult thing I've faced is to keep myself motivated. The dreams we dream don't just come true. Our reality is totally different from our dreams.
Well I think our motivation gets sapped when we give up on our dreams. If you try following your dreams and actually going for it you will have motivation for it because it is your dream and if you fail you will not regret trying for that dream.
Seek inspiration every day. Focus on the emotional reward you will get. Track your goals weekly and periodically. Set a reward for yourself. Find someone to hold you accountable for your goals.