I had this at uni. It was a long time ago, so I can't really provide references.

If you want to learn something new, you need to reinforce each time

When you already know you can do the whole thing, then it's a good idea to start intermittent reinforcement. It should gradually go from 100% to 0% rewards, so you could e.g. take a d10 and roll it; first week anything over 1 gives you the reward, second week - anything over 2 etc. The die is essential, you need to randomize the reward, not just say "every 1 out of 4 gets a reward" - that in fact works worse than 100% rewards.

I used it to potty train my kids, worked like a charm.