While some may question the wisdom of it, I found building the airplane (or preparing to build it) during flight training really motivated me, particularly when I was plugging down money on renting a plane.
Money was an issue for my endeavors; fortunately, I had a solid plan going into it. I worked a second job and put aside the cash for about half a year for training - I didn't want to have to hold that up owing to a shortage of funds - and then started putting aside for the aircraft, knowing that I could continue to save for the engine while I worked on the airframe.
It's about priority. I could spend four bucks on a cup of coffee....or I could buy an AN4 bolt. Buy a game off of Steam or an airspeed indicator. Etc., etc.
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Above all, the wife's support was key. She has absolutely no interest in General Aviation at all, but since it's important to me, it's important to her. Indeed, she'll sometimes ask why I haven't gone out to the airport to either work on the plane (there is always something to do on it) or go fly!