Some things you learn without really trying. We learn our native language by repetition because we hear it all around us. But the question here is what if you want to or need to learn something you won't learn automatically? What helps? Try spaced repetition. It doesn't happen every day automatically. You must force yourself to do it even though it is tedious, if you want to learn what you want to learn.
I think what GP meant is that we already learn a lot of things through "spaced repetition" even if we're not consciously applying that technique. E.g. if you drive the same route repeatedly, eventually you'll remember the way without needing to look at a map. That's spaced repetition.
