Well, to be honest. I have these kind of moments all the time. I'll be in the middle of a huge project, then all of a sudden, I think to myself. "What am I doing and why am I even building this?" I'm the kind of guy who will be almost completely finished with a large project and then notice one tiny little thing that no one else would probably notice but if I'm not happy with it, I'll have to take it completely apart and start all over once again. It happens to me with almost every build.
For example, I've been working on my entry for the "Castle" category for the CCCX and I've at least started over 6 times. It can get a bit frustrating at time's but I guess I'm just a perfectionist!
Oh, well, we all have are building styles.