> Perfect square doesn't happen.

This. Whenever I'm feeling like my own work isn't as perfect as I'd like, I go look at the sheds on display at Home Depot or Lowes, or look at the framing of a professionally-built new construction home... it's all way worse than what I did for my shed/workshop!

Caulk, trim, and drywall will cover up a heck of a lot, and professionally-built structures rely on this fact quite a bit as well.

Working with lumber is an imperfect endeavor anyway... Despite my best attempts to get pieces that are actually straight and not full of moisture ("KD" stamp doesn't seem to mean much these days), I've had a lot warp/twist/shrink by the time I get it cut and assembled. All within a usable tolerance though. I see the same or worse in other structures I look at.