Mike, My situation is different from yours in terms of ultimate motivation. I am an artist using wood furniture as my medium. My two main motivations are the mortgage and creating as an artist. I make a meager, but growing, living as a furniture maker/artist. if your woodworking is a hobby, and you make your living at something else, then your motivation is something other than to make money. Although, it may not exclude making money. So a close cousin to "motivation" is "inspiration". Some woodworkers look for inspiration as to what they make next.
I have been an artist all my life and have never wanted for inspiration. Now this is not a brag or a "nah na na nah na" It is just that "inspiration" truly comes from working. I love this quote by the artist, Chuck Close. The paraphrased version of his quote (which is actually a short article) is..." inspiration is for amatuers. Inspiration comes from getting up and going to work. The work inspires itself". This is worth looking up as I am badly paraphrasing it.
So, how does this apply to the non-professional woodworker? All I know is that as you make something, ideas come up as you go along the construction process. If you use pre-generated plans, much of the spontinaity and opportunity for "inspiration" may be lost, and all you are doing is going through a set of motions.
I don't know if you are a plans man or not. A suggestion as an excersise....pick something you know how to build or have built before. A small wall cabinet, a small table, a box etc. Then go to your shop and build it straight out of your head, with no plans. Make radical changes as you progress through construction if you think they are needed. Add to, subtract from.......all leading to discovery and inspiration..
So there you go ......DISCOVERY and INSPIRATION are your MOTIVATION to create.
neil