Where did my positive attitude go?

I see myself as a positive person most of the time. I see the glass as half-full. I try to see the best in other people. I look at the bright side most of the time. But for some reason, I have fallen into a negativity funk and feel sad. I'm not really sure the cause of this sad feeling. I can usually pull myself out of feeling sad pretty easily. But for the last few days I have not been able to put on my happy face. I'm going to pray about it.

What do you do when you feel sad, depressed or negative thoughts consume you?