Watching Christmas come and go can be a tricky thing emotionally. Some people experience 2 or 3 or 5 different family Christmas celebrations, plus work gatherings, church events, school programs, and more. There is a LOT of momentum that goes into preparing for Christmas, but very little preparation for "coming down" off of Christmas.
This can feel very much like over-eating. There is a fullness that is not necessarily comfortable or satisfying. Yet you are still hungry, because you've gotten accustomed to eating. Too much activity and celebration can feel the same way.
Let me encourage you to follow the Bible's lead on this...and "be still." It is ok to sit and reflect. It is even ok to feel sad or 'let down' after all of the events. It is ok to grieve a little over things or people you missed during the holiday season. It is more than ok to "be still and know that I am God." God sees you in your loneliness, your stress, your winter depression, your dysfunction, your hopefulness, and even in your joy. He wants you to take comfort in His all-knowing presence and peace. He is God!
I hope you are able to move forward and find traction after the hustle-bustle of Christmas. Immanuel, God with us, came so that we could experience Him - His joy, peace, hope, and life-giving salvation. May you be found as a 'wise man' who seeks Him each day of the new year.