Loneliness is an emotion caused by chemicals in the brain. Like all emotions it has it's roots in the evolutionary survival process. It kicks in to cause you to seek companions to help fight the saber tooth tigers. Although the danger is no longer real the emotions are still there. They are a hold over from our ancestral days just like the appendix. Holidays intensify them because seeing others gathering together creates the fear that the tigers will select you who is by yourself for their next meal. How to deal with it? Accept it as a sign that everything is functioning in your brain the way it should. The moment you no longer feel this emotion then you may be on your way out of this world because something is wrong in the brain.