Whether it is your mood or someone else’s I find the following 6 tips to be helpful in dealing…
1) Acceptance: It is ok to not always be happy. Just like the weather, it isn’t always a sunny day.  This is part of what makes the world and humans perfect and complete. Sometimes simply honoring our feelings and allowing ourselves to feel how we feel is all we need.
2) Understand the Cause: Are you simply hormonal or tired? Are you trying to blame others with reasons for feeling down?
Or is there something deeper and bigger in there that keeps coming up?  The usual suspect for a deeper cause is fear.  Any negativity that arises within can usually be traced back to some sort of fear response if we pay enough attention.
3) Ask the Mood What it Needs: Often we are better at complaining than actually looking for a solution.  Challenge your mood to see if it actually has a need that can be satisfied or if it just wants to be upset.  If the mood say’s “I’m not good enough” ask it, “what do you need to know, or do to be able to know that you are good enough?”
4) Honor the Mood: When we reject or get frustrated with ourselves or others for being in a bad mood, we are simply making it worse.  It’s like telling someone that is upset that they are an awful person too.  It doesn’t help anything. Moods come and go like waves, and when we hate on the mood, it will feel worse and stay around much longer!
5) Love on Yourself: Step into your wiser self and see your mood for the fear that it is. As your adult, loving, wise self see your fear more clearly and talk to it like a scared little child that needs reassurance, “It’s ok that you feel alone…I love you, you’re ok.”
6) Acceptance Again: Don’t confuse acceptance with helplessness.  Acceptance is the simple understanding that it is ok to feel how we are feeling, and that if we don’t hate on ourselves and make it worse,  the feeling will go as easily as it came.