One: I was impatient and didn't prime a bookcase and realized that under the lovely latex paint was an oil based varathane. Oil and water do not mix and you get a lovely paint that just peels off. I like to think of myself as a seasoned painter and have never done this. Rushing and skipping the most important step of priming just gives you more work.
Second glitch: The paint color reminded me of doggy doo or of a lovely glossy 70's brown. Instead of heading to the big box hardware store I hit my favourite paint store: Benjamin Moore. Their paint and expertise is worth every penny. I told the consultant my sad story and she happened to have a mis-tint that was just the colour I was looking for and it was only $5! I love a good bargain.
A few coats later and the dresser looks fantastic. The sad stinky white desk looks polished and the bookcase.....well...still scraping off the paint.