January 
This went well! I will need to replenish soon if I want to continue, and it looks like it makes sense to - I feel like my immunity has improved a bit, and (together with figuring and eliminating some environmental factors) I was able to get over a chronic cough that bothered me over recent few months. (Not medical advice, but the correlation seems to have been widely established in authoritative sources.)
For February, I am choosing the goal that I started a few days ago to try out the setup: tbr_started_whittle. The background is that I tend to start many books at once and unless I am pushed to finish by a deadline (ARC publication date or library due date) I tend to get excited to start something else, and keep multiple books in the limbo of “I would like to finish this one day, no reason not to be planning so…” So, this goal gets the sum of percentages of the unread portions in all my books that have been started (past 15%), and I am planning to be actively reducing this total (which started at 9 full books - consisting of multiple partially read, of course) down to 5 by the end of February and then keeping it under the flat line of 5.