I'm right there with you.... I don't know how many times I've sanded the same spots over and over. Then every time I shoot primer on I see a bunch more flaws. I think having the eye and feel for the various defects before you apply even primer is what really sets apart a pro from a amateur.
There are two trains of thought in regards to keeping your sanity while doing body work. 1) That you keep working the same spot (e.g. the decklid) until it's complete to give yourself a sense of accomplishment. Or 2) Keep moving around so you don't drive yourself crazy on the one spot.
I did the moving around a lot, trying to get both doors and 1 quarter done and it's tough because you don't feel like you're getting anywhere. The one good thing about moving around a lot is that I could apply filler to multiple spots and sand one while the other spots where drying, etc.
Hang in there... just keep reminding yourself how sweet the car is going to be when you're done!!!!
Travis
72 Cuda