Get some friends together for a good sing, serious or silly, it doesn't matter. Music stimulates the brain, singing is good physically and emotionally, especially with other people.
Learn something new. There is a huge amount of online courses available for free, where you can efficiently take classes from top universities in the world, working in your own pace. Here's a few you can try.
You can also learn new language. There is a great (and absolutely free!) platform called Duolingo. Check it out!
1. Get some good binoculars - or better still a telescope - and look at the moon. 2. Go on the internet and find some great origami designs to make. 3. Write a short story or article and publish it online.
All the great answers I read here, thank you for your advice, guys :) Just would like to add few tips as well: Download "smule"Sing! application and enjoy singing your favourite songs, great fun! Don't worry if you don't have a perfect voice, it makes your voice very beautiful! And of course, my other advice would be art-related, as art is the best mood-booster and inspiration for me. Call up your friends and visit a good art museum together!
If your mind is turning to how you'd like your 2017 to turn out, then this quiet period between Christmas and New Year is perfect to start assembling that vision – literally. I'm a huge fan of the post-festive vision board.
Everyone I recommend this to will say the idea sounds absolutely ridiculous... until they try it. So why not just call it a 'goal collage' if that sounds less weird? I would post a YouTube video on the subject but they're all terrible and seem to be claiming there's some kind of literal magic at play. Creating a compilation of physical images (Pinterest just won't cut it) that represent the changes you'd like to see is merely psychological spring-cleaning. It'll help define the things at which you should – and shouldn't – be aiming your sights in the months to come.
Whether it's career development, new digs, fitness plans, a gussied-up love life or all of the above; once you've decided something matters enough to be located, printed or cut out and stuck down, you'll be able to take a step back from what's you've created and see a bigger picture on which to focus. Just remember to write everything in the present tense or your brain will think it'll never actually happen (the trick is to con yourself into confidence). Should you revisit your masterpiece in 12 months' time, you'll be amazed by what you – yes you, not Gandalf or whoever – made materialise.