Frustration
What got me the most was the guilt of spending money on the car. If I was buying part and making progress I got frustrated and I couldnt look at the car and say I only need this and this before I can drive it. I would look at it and say I need these 3 pages worth of parts before its perfect.
I ended up trading the Dart for a running driving car knowing if I had something that drove I wouldnt be as concerned with it being perfect. To bad the car I got in trade had hidden frame rot that was unfixable.
Stick with it. Doing it yourself means you know it was done righ and theres no frame rail holes filled with bondo.