6 month roller coaster ride

It's been six months today I've had my new supervisor job. A lot of times I never thought I'd make it this long (and I still am not sure I'll make it a year).
It's been up and down, nonstop, just when things look better something happens, or someone does something, and I'm back to losing sleep. My bosses, who I should be able to rely on for support, sometimes seem to be trying to make things tougher for me.
Just a couple of days ago one of my key people said he might leave for another job, which would mean no vacations or days off for me until I trained someone else. Now it looks like he's staying (I really hope), but the big bosses have played with him like all of us.
I've never been into doing sweats, but maybe it would help with the stress.
Things are looking better right now, but I'll wait and see. I've been there before.