Somewhere in the vastnesses of the Internet and the almost equally impenetrable thicket of my bookmark collection, there is a post by someone who was learning Zen meditation...
Someone who was surprised by how many of the thoughts that crossed his mind, as he tried to meditate, were old thoughts - thoughts he had thunk many times before. He was successful in banishing these old thoughts, but did he succeed in meditating? No; once the comfortable routine thoughts were banished, new and interesting and more distracting thoughts began to cross his mind instead.
I was struck, on reading this, how much of my life I had allowed to fall into routine patterns. Once you actually see that, it takes on a nightmarish quality: You can imagine your fraction of novelty diminishing and diminishing, so slowly you never take alarm, until finally you spend until the end of time watching the same videos over and over again, and thinking the same thoughts each time.
Sometime in the next week - January 1st if you have that available, or maybe January 3rd or 4th if the weekend is more convenient - I suggest you hold a New Day, where you don't do anything old.
Don't read any book you've read before. Don't read any author you've read before. Don't visit any website you've visited before. Don't play any game you've played before. Don't listen to familiar music that you already know you'll like. If you go on a walk, walk along a new path even if you have to drive to a different part of the city for your walk. Don't go to any restaurant you've been to before, order a dish that you haven't had before. Talk to new people (even if you have to find them in an IRC channel) about something you don't spend much time discussing.
And most of all, if you become aware of yourself musing on any thought you've thunk before, then muse on something else. Rehearse no old grievances, replay no old fantasies.
If it works, you could make it a holiday tradition, and do it every New Year.