Difficulty tends to climb right before something ends, and that is a design feature rather than a sign you took a wrong turn. The hardest part sits at the end because everything before it was preparing you for it. When a thing suddenly feels heavier than it did last month, that often means you are close.

Before you decide you are stuck, check where you actually are, the week of the term, the page count, the remaining reps. Distance left is usually shorter than difficulty suggests. Then make one more attempt using what the last attempt taught you.