Having A Bad Day After Actually Having A Few Good...

I was just thinking yesterday, wow, I've actually felt pretty good since Friday, which is 4 days in a row!  Not dance in the street happy, but not suffocatingly depressed either.  Friday our town had city wide rummage sales (small town) and my dog and I walked all over to most of them, it was a beautiful day.  Saturday we went to my sister's and my grandniece who is 2 can cheer anybody up.  Sunday was Mother's Day and though my son and I had planned on going to a movie, I went flower shopping and it got too late.  He was happy not having to go to his dad's for the day.  Yesterday I planted the flowers I bought, another beautiful day.  I was so tired last night I fell asleep 10 minutes before the end of my favorite TV show, which was the season finale, which bummed me out but my dad has DVR service so I had the good sense to set that in case I missed it so I can watch it again.  Then my son informs me he's getting an F in math, math is his best subject, he joined Math Wizards and brought home a first and second place trophy so I couldn't understand that!  He told me he hasn't been handing in his assignments.  He begged me not to get mad but it was really hard not to.  I did tell him to talk to his teacher and that I would help him in any way I could to help him get caught up.  Today I woke up down, maybe because I didn't sleep well after my nap and his announcement.  So I guess my stretch of good days is over for now at least.  The sad part is that even though I was keeping my mind occupied and doing things I enjoyed, I still wasn't HAPPY.  The depression is still there, running like an undercurrent in my life.  Today as I write this, my heart is racing and my anxiety is kicking up and I don't know why.  I wish I could have more than just a few good, or almost good days, I wish I could be HAPPY!  Why can't' someone cure this awful disease???