Why?

So last night I was happy.  Got good news yesterday and today I am off work until 5pm and will have the house to myself for a few hours without my youngest son sulking about on video games and refusing to speak to anyone.  Have no pressing projects to do.  Studying is over.  House is semi clean.  Turned the sprinklers off for the year so yard work done.  Should be a day of no worries and just relax.
Then this morning I woke up with a headache, but was able to take some medicine and lay back down for an hour.  Instead of relaxing my stress level has sky rocketed and back in panic attack mode.  Have no idea why.  Can't nail down anything truly pressing that I am freaking out about.  Usually I can at least name a reason.
So wanted a nice relaxing day.  Hate it when I do this to myself.  Sigh.