Not all days off can be categorized as sick days or vacation days.
Most companies have time-off days divided into sick days and vacation days. I think that's a little too black and white.
I've always wondered where doctors' appointments fall. What if you're just going in for a check-up? It's technically not a sick day, and it's most definitely not a vacation day. And it always feels a little strange to schedule a "sick" day a week ahead of time. I know it's just paranoid, but I always think there's some HR person whose sole duty is to examine requested days off and when she sees something like that she makes a note in my personnel file, e.g., "Employee knows days in advance that she's going to be sick."
But even if you get past all that, I think there should be a category for those days when you just need to chill. One cool boss I had called these "mental health days."
It would be so much less stressful than having to call in and lie about your smallpox flaring up or fake a raspy, strep throat voice even though you're claiming you sprained your ankle.
I used to take a day off every once in a while when my son was little and was in school and my husband was at work. I would just spend a day alone at home, watching old movies and recharging my batteries. It worked wonders. I think it was more effective at easing tension than going away for a whole week and all the scrambling to complete work before and catch up afterwards that comes with that.
What do you think? Would your bosses be amenable to something like that?