It's not a "serious" mood crash, almost certainly not worse than with the darned thing in, but there tends to be a trend when you have it removed. Usually the first week you feel GREAT and lose between 2-5 pounds, the second week you still feel better at first, but about day 10 you can get very low and snippy. No energy, bad mood, start thinking "This is how I felt with it IN, so it MUST NOT have been the Mirena". Stick with it, within a week or so of hitting this "mood crash" you start to feel better again.