There has been one principle false analogy about memory, namely: "Memory is like a muscle." This false analogy has influenced the concept of memory as something that can be improved. It seems to make sense. Even in your life, you may be able to recall that trying to memorize things actually makes you better at it. But that's not what actually happened but you think it did. (Psychologists call this confirmation bias, the tendency to see things the way you want to see it.)
Hundreds of psychological experiments have concluded that memory is not in anyway like a muscle. It doesn't matter how much you try to practice it, you are stuck with the memory you have. It simply won't get better. Psychology, unfortunately, can't explain why this is.
Neuroscience can. Memory is simply the connection of neurons. When you form a new memory, your neurons connect to new neurons. This has no effect or influence on your memory "system". (The connection of new neurons is also the definition of learning; memory and learning are the same thing.)
So if you are practicing the piano and want to memorize Brahm's Lullaby, you'll need to repeat it hundreds of times if you're an amateur. The more you repeat that specific memory, the stronger the connection between neurons, but it will only be strong for that specific memory allowing you to recall and play the piece with ease. However, it will not make your memory of yesterday's dinner any stronger no matter how much you practiced memorizing piano pieces.
So, what did you have for dinner, yesterday?