[[id:05a39f96-fb1c-4d71-9be1-fc4c2e251e8f][Start small and improve later]] by practicing over small units, make the unit per practice bigger, and repeat until you're confident to move on to other topics.
For example, say you want to be efficient with competitive coding.
You can start with solving only one problem per 3 days for a week.
Then, you can go with 2 problems per week, then 3, then 4, and so forth.
There are various tools to practice spaced repetition with Anki is one of the most popular tool.
If you're using [[id:c422175a-5b65-4311-8cc6-11efd55364e8][Org mode]], org-drill is a plugin that builds on top of it to implement a spaced repetition memory system.