It's all psychological. Yet any arbitrary event which seems to carry the promise of a new beginning is alluring. There's something transcendent and powerful about being able to cast aside old worries, fears and other emotional junk, and be able to start fresh. Deep sigh of personal satisfaction. A birthday, an anniversary, New Year's Eve, a personal or social rite of passage -- any of these can give us reason to pause, consider, and redirect our lives. It is a distinctly human and touching ritual.
It's all arbitrary, of course. I could randomly choose a date, or a given hour each day, on which to rededicate myself to my personal goals, or even change those goals. That does not detract from the importance of the act.
So Happy New Year, one and all -- just for fun, here is Wikipedia's article on how New Year's Eve is celebrated around the world. May the new year bring to each uf us our heart's desire.