I’ve been making a mistake all my life, and as a result have run into the same (and now obvious) problem.
Let’s say you have a piece of written material to memorize. Like most, I start at the beginning of a piece, memorize the first bit, then work to memorize everything after it one section at a time.
You tend to nail the beginning, but then the memory and preparation of the latter part isn’t as great. Likewise, some people memorize certain key chunks of the piece, then fill in their memory of the rest later. They still run into the same problem, nailing the key parts while their memory of the transitional parts isn’t as solid.
It can slow you down in practice or, even worse, performance. Unless you’ve got the piece on lock in your mind, you can hit a spot you don’t know as well, forget and draw a blank. The terror of the moment can even prevent you from comfortably jumping to a subsequent section you might know better. This is probably the one aspect of performing work from memory that has always terrified me the most.
In the rest of our lives, we learn that a key to success is to start with an end goal and figure out step by step how you get there. Often, by backtracking or working backwards, you better piece together how to get to that goal. (This also helps you find stuff you lost)
Likewise, it finally occurred to me to try backtracking in memorization. Start by memorizing the end of a piece, either the last sentence, paragraph or whatever section you can comfortably put on lock in a short period of time. Then go back to the previous section, learn that, and then recite the two parts together.
Any struggle to do the first section from memory is rewarded with the momentum of a subsequent section you know well. You gain momentum as you do the piece, rather than losing momentum from subsequent parts being more unfamiliar.
I’m glad I finally started learning pieces backwards. You might want to give it a shot.