When you first start dating someone, you can never imagine how your lives will look together a decade later. But by the time that rolls around, you know all of each others' habits, quirks, likes, and dislikes. When you're in love, flaws don't seem to matter. That's probably why married people write so many funny tweets about their married life — you suddenly start noticing all the little habits that you hadn't picked up on previously! Adding kids or pets to the mix certainly changes up the dyna…