My favorite stress buster is walking bare foot on the grass in the backyard, somehow the cool feel of grass has a magical effect of calming the body.

Try it and feel the difference. I think our bodies are created to be in sync with nature  while life  today take us more & more away from it.

When doing the same routine everyday, the brain goes on auto pilot and fails to notice the things around and w/o that stimuli, things go boring.

So introduce a small change everyday by changing the parameters. Say take a different route to work. You will be amazed at the difference. Suddenly you start noticing the trees, the smells and even the streets. Suddendly brain gets a different experience and it starts analyzing with result being you are in a better mood when you reach office.

Although we presume that we act because of the way we feel, in fact we often feel because of the way we act. As such to change our feelings we should change the way we act. Try a smile when you feel low and you will see that  simple act can start to change your mood.