When two people fall in love, they only see sunshine and rainbows when they look into each other's eyes. If you asked, "What's the worst trait of your boyfriend or girlfriend?" they would answer, "Absolutely, positively nothing!"
Ask that same question a few years later when they're living together and have seen each other at their respective worst. You'll get a pretty good list:
"She cuts her toenails on the coffee table."
"He speaks in a cutesy voice on behalf of the dog."
"She kicks me in her sleep."
Hopefully none of these nuisances find their way into your work life, but other ones probably do. Everyone has some weaknesses in their work behavior that they need to work on, and they often extend beyond annoyances (such as eating a smelly lunch at your desk) and become problems for your career.