Excitement seems sporatic, temporary, often experienced as short bursts of joy and happiness. Motivation actually depends on the presence of excitement . . . the lure of that which we love to do, consider, plan toward, have at the ready in life.
First, determine exactly what it is that does excite. Singing, painting, volunteering, counseling, gardening, dancing, cooking, skiing, conversation, racing, viewing some type of action performed by others. Even watching others who are doing what we love can generate pleasure.
So then, why not find a way to enter this happy, highly productive state of being? Begin with finding out what it is that produces excitement within the heart and mind -- then go toward it with steady or speedy motion -- in any style you prefer.
This is, simply, the Answer to Everything.