I am a believer, in spite of experience and evidence, that form follows function. A thing should work well, and that is more important than how it looks. Every day something happens to disprove that, but still I row against the current. I'm not proud of it necessarily, it's just a habit.
The most common failure mode for me goes like this: I spend quite a bit of time designing something (good), then building it (good), then tweaking it to make it work (good), then I forget to clean up the environment or the thing itself and it looks like a minor disaster (bad)—even if the thing itself works like a dream.
That impression a person gets when they see or hear or smell something before they can touch it or taste it colors the rest of the experience. Build some shelves but leave the room a mess because you'll get that part tomorrow? You'll have to answer for that—not just the mess, but maybe some questions about the efficacy of the perfectly good shelves. Build some shelves but move the mess into a different room and you'll get that part tomorrow? You're a hero who makes the best shelves. Perhaps the best solution yet is to build the thing and clean the mess, but not every project fits neatly in the space of time before the rest of the world—or at least the part of the world that matters—sees the results.