I agree that 'must see everything' is often a route to sadness. I usually either have a specific thing I'm there to see (and will putter at things on the way there, or whatever amuses me after) or am there to just ramble and I see what I see.

(I cannot actually go around museums with my mother, though, because she will stop and take forever, and I do usually want to see more things than that allows.)

I also agree with your theories for looking at things other people are not looking at, both on the practical and philosophical levels.