Oh, I hear ya on this one! We only got about 2 inches of snow yesterday, so I shoveled and then later in the day went to the gym for 30 min of cardio (dr. recommends 30 min of cardio at least 3x week). I've been feeling pretty good the last couple of weeks (excluding my sleep) and I felt fine all day yesterday. Paying for it now though. Horrible sleep last night and mild headache and subtle dizziness today. Ugh! Learning lessons the hard way.