When the sick day really isn’t one, how do you explain it?

Question: “Like many companies, mine differentiates between sick time and personal time. Sometimes, I wake up in the morning and just feel like spending the day at home or running errands, but because we’re supposed to schedule personal time in advance, I’m stuck with having to invent an illness or some emergency. How can I just take a spur-of-the-moment ‘well’ day without having to lie and feel ridiculous?” – Marla, Bel Air, Md.