What is the right method to practice origami? Is rote-memorization correct method? I love to find and learn Origami toys, but I can't memorize the steps. 

I often manage to learn models or just while playing with papers I discover a new model; if I stop practicing them for a few weeks, I forget them.

So, how do artists memorize the origami steps? Do they repeat one model again and again and again? I can recall, once, quite accidentally I made (own, new) a butterfly which can be hung on wall-hook in 'wings open' formation. It can also be inserted at a slit as 'wing closed' formation. But just a few days later I had to almost completely re-discover the steps. To make it fluent, I had to repeatedly practice it again and again, on several (3 or 4) days; and I still need a revision at an interval of a few months. 

I think I'm able to feel to-some-extent the symmetry, patterns and 'fit'-s. But when level of complication goes slightly up, I can't hold them at mind together, and I need to enter cramming or rote.

In contrast, I've seen, many people including cheerful tiny kids, can effortlessly memorize the fold sequences for long times. So I guess; I'm doing something wrong way. (And I've seen in any subject or fields I've to apply any rote memorization or cramming, I did very bad, accumulate some headache, and forget all informations within minutes). So I guess those peoples (including cheerful kids) not using rote memorization. Am I right?

Or rote learning (cramming) is the way kids do? Could it be  method that artists uses?

P.S. 

I have problems with mental arithmetic, and have a very lousy short term memory. I fail to hold multiple bits of information at the same time.
It's because you are still at a stage of learning where you are simply memorizing a series of steps, without really understanding the more nuanced principles of and techniques of origami and how these forms are constructed. 

In neuroscience, it's called 'chunking', and it's a crucial part of becoming proficient at any skill, and it only comes with repetition, study, and practice. With more nuanced learning, instead of memorizing the simple mechanics ("fold this, then this half way, flip over and tuck back"), you'll start thinking in the patterns and techniques that combine a relatively simple variety of folds to make increasingly intricate designs. 

Think of it like cooking. You can follow (or memorize) a recipe and cook a chicken dish that you can prepare over and over without any real understanding or context. But once you learn the more intricate principles and science behind cooking, you start to understand why things are done that way &mdash; so now you are no longer blindly following a series of steps, but following the patterns and techniques you learned to achieve the desired result. Now when it comes time to "memorize" yet another recipe (or come up with a creation of your own), you'll already know about 90% of it before you even begin. That is how you build a repertoire of dozens, sometimes hundreds, of "recipes" without having to memorize each step of each individual creation without context.

The same goes for the techniques of origami.