Is there any way you could give yourself a precommitment? You said you want to pass the Chinese proficiency exam by 2017; can you take the time/money to register for it now, ahead of time? If you know that you are already on the hook to take the test "January 16th at 3pm" you would be motivated to not waste that investment.

I have been using Duolingo to learn Spanish. However, I also struggled with practicing as much/as frequently as I wanted. I started minding it using Beeminder's data integration, which has so far kept me consistent.

I think what is benefiting me is the positive reinforcement of Duolingo's "earning points and leveling up, yay!" plus the threat of losing money if I don't meet my targets in Beeminder (even though I do not yet have money pledged to the goal, I know that I would commit to do so after my first derailment).