What has worked well for me is to have 3 cars. All different, one daily driver, one drag car, one street rod. I then work on the one that I have a passion for at the time, and as time goes on I move back and forth between the 3. I have invested well under 30K in all three cars so it isn't like I have a ton of money and can afford three projects. I view it as one project, just a different car as my liking takes it each couple months.