Go to 10 meetups in a month
I find it reasonably easy to chat with strangers, but incredibly difficult to take that chatting to the next level of friendly acquaintanceship. Also, I learned my limit for cold professional networking events is 29 minutes and thirty seconds.
No sweets
The first 10 days of this month were, ahem, a piece of cake. I had thought this was supposed to be a challenge? But then I was punished for my hubris with two weeks of intense cravings for processed sugar. I ate a ton of fruit and simple starches like saltines and white corn chips to try to fill the void, and I'm sure I actually ate worse than if I just allowed myself a piece of chocolate.
Study Spanish
I learned some Spanish. After trying a variety of sites, I settled on Duolingo, which is free. The learning is all gamified, and I respond well to virtual xp and gold stars and level ups. Too many role-playing games in my past, perhaps.