On average, most forget about 50% of what they've read after 1 hour, and only remember 2% after a week.

It sounds like your problem has more to do with retrieval. You _learn_ something when you retrieve something from your working memory or long-term memory (you build myelin, a fatty substance that isolates your synapses, which enables you to later retrieve the information).

The optimal way to learn is to use spaced repetition. It naturally happens if you apply the knowledge frequently, or you can use a flashcard app to track it.

If you struggle to _understand_ something, it often has to do with overwhelming your working memory. You are connecting several concepts that you don't understand. On average, most can keep seven items in their working memory, but after that, you'll start feeling lost.

When you internalize a few concepts by retrieving them, followed by a long break or sleep, you free your working memory to connect more concepts.

You don't internalize concepts by retrieving them from memory, you internalize concepts by reconstructing them without aids like flash cards. Otherwise you just connect the words and not the concepts.

Spaced repetition in form of testing yourself. Anki and other software help with this.

The best way to learn concepts is to first forget them and then reconstruct the facts based on previous knowledge. Spaced repetition actively hinders this process by trying to ensure that you don't forget. It is great for shallow knowledge like language, but if you are doing it for maths or programming you are just hurting yourself. That type of training is how you get people who can talk like a champ but can't even solve fizzbuzz.

It depends. Spaced repetition can be used to mindlessly memorize formulas, which I agree is not useful. Or it can be used in the way described in this article (http://cognitivemedium.com/srs-mathematics), which can lead to a deeper understanding.

See Ebbinghaus' Forgetting Curve. [1]

[1] https://www.inc.com/scott-mautz/train-your-brain-to-remember...

Same for me - this can be called the "Illusion of Competence" and is discussed by Barbara Oakley in her book "Learning How to Learn."

Do you have any process to try to internalize learnings better?

Practice. That means both doing problem sets and teaching others (or thinking through the content as if you are teaching, so ask lots of questions and think about how the concepts fit into other ideas).

At the moment I’m working through CLRS intro to algorithms. There’s some math in there and derivations. I tend to run through the derivations separately while I’m working through the content to really internalise them (and I just enjoy the math). The author is nice enough to provide extensive problems to solve too.

Similar can be said of The Art of Programming. Plenty of maths in there to follow along with and plenty of problems to solve.

In addition, don’t be afraid of revisiting content. If you read over a text once but don’t fully internalise it, you hopefully have gained enough knowledge to have an idea of when it might be useful to you. So when you’re working, go back to the text and read through what’s useful and implement that.