I was lucky enough to have a really memorable experience with "how it looks on the hanger isn't how it looks on" age the age of 9. My very favorite dress that year was like that. So that knowledge stuck with me forever.

The down side of this is that I often try on hideous things thinking, "Maybe they'll be like that blue dress when I was 9! and look really awesome on!" And then no. But still, better not to miss out.