Talking about feeling down or sign of depression, should think of the root cause.
One of the friends I know - JYC (basically just met him one time but read his emails, thoughts, blogs, discussions, arguments for many many times) emailed me this:
Life is easy, just take it one step at a time and never look back.
As human, we can't avoid not to look back. Even u do look back from time to time, just look back enough that it goes as far as it is pinching your heart, not breaking it. Put a note where the page is, mend it, and then go further.
Depression is a like a bottle of salt... U can only handle a pinchful, and that pinchful makes your life more tastier...
Chinese people, we always talk about "pouring salt on the wound" to make it worse or known as some "stupid wounds" that will never heal. Think at the positive side, why not using the idea from JYC "handle the salt a pinchful, and that pinchful makes your life more tastier..."
JYC, thanks for your thought.