I've given up on a couple. I had one custom build ( a stretched VW bus with a wicked small block Chevrolet) that just went waaaaaaaaaaaaaaaaaaaaaay too far into left field and had to take a step back and re-examine things. In the end I scrapped the whole idea. Too many mods and it started getting way too engineered.

Another one was the AMT 66 Barracuda Hemi Under Glass kit. I just couldn't get this thing to look the way I wanted to. So many discrepancies with the kit and really too much for me to take on at the time.

I really try hard to finish anything challenging but these two were beyond my patience (and I've got a LOT of that) for the Barracuda kit and things just got too deep on the custom build. I've learned not to go too wild in order not to exceed my limitations.