Pushing on through Challenges 13-14 is the best thing I did. The phrases are repeated and embedded multiple times in the following challenges so I certainly think that helps if you were to repeat challenges 13-14.
It’s sometimes worth dividing a challenge in half, leaving the second part until tomorrow. Each challenge is very intense. Think about it: you have to respond about 5 or so times per minute, so within one challenge that’s roughly 150 responses in a new language in half an hour. That’s very intense.
Also I found that taking a complete break from it for a couple of days often helps.
And yes, pushing on and then coming back to it is also a good approach.
And any combination of the above.
Whatever works is right for you.
Thanks for sharing your woes last year this has helped me with wondering whether to go on or go over the challenges first.