Making the effort to apply the Feynman Technique will ultimately save you time and energy, and allow you to solidify your understanding of new knowledge. From there, you can concentrate on using it.
This technique was named after physicist Richard Feynman, who invented it.
After you feel like you've learned something, apply these 3 steps:
Pretend to teach it to a child. This will force you to simplify what you’ve learned, to come up with clear analogies, to make your explanation complete but short, and to avoid jargon.
Find the gaps and fill them in. Doing step 1, you’ll realize you struggle to explain some areas of what you've learned; there are some gaps. Go back to your learning material and re-learn what you missed.
Repeat the whole process till you’ve got it down pat. (You could then give yourself a final "test" by actually teaching it to someone who has absolutely no prior knowledge of the subject.)
The crux is that it’s impossible to teach something complex to a complete beginner (ideally a child) without fully grasping it yourself.
This technique forces you to examine your assumptions, to recognize the first principles and building blocks of something, and to analyze your own thinking.
In addition to understanding a subject better this way, you will also retain it better. This kind of deep processing is key to mastery of a subject.