Hey there, how are you feeling today?

I tend to agree with BNLsMOM - we often cannot just change our attitude and will ourselves out of this slump. I find we can however change our environment, which can have a positive affect on our moods and BP. If you cannot focus, get up and go for a walk, have coffee with a friend, watch funny movies on You tube... anything, but do not let yourself become absorbed by your thoughts.
When you are down, you tend to become introspective, then start feeling sorry for yourself and land up in a horrible spiral. Do not let your thoughts start going down this road. Keep yourself occupied in other ways.
Maybe try take part in sport - which also releases serotonin