On my journey of aiming to live well with chronic pain, I go back and forth between happy and sad. But who doesn't? Life isn't always happy and it isn't meant to be. There are events in life that no one can escape: illness, death, loss. Its all part of the circle of life!
Despite the holidays, people still deal with ups and downs. It's not always all holly jolly.
Many try to deny the fact that life is about ups and downs. We tend to think that we have to achieve "_____" (enter whatever you like) and then life will be happy and perfect. That's not the way it is.
The secret to being happy is letting yourself be the opposite of that from time to time without giving yourself a hard time about it. If you are sad, be sad. If you are afraid, be afraid. If you miss someone or something you lost, miss them. It is important to let yourself pass through all your feelings, so you can get back to the good stuff.
So, if you have a day where you are really in pain and life feel like life has nothing to offer you, feel it. Don't deny it. Everyone has those days and it is ok. If you ignore how you feel, feelings may be subdued but they will surely manifest in other ways.
Feel whatever it is that you feel, and then move on. That is the flow of life, and a secret to happiness.