I’m beginning to think someone cannot possibly learn anything without the brain giving the green light that it will be useful in the future (like those random facts you never think about but are handy in a conversation) or until you force the brain to think the information will be needed, but you must continuously think about it sporadically.
Take into account how you read a sentence and in a few minutes you cannot properly reconstruct it again in your mind, unless a musical tone is accompanying it—this helps facilitate the learning of it, which is why you can remember the lyrics to a song from years ago and not what you talked with your best friend the week before—or you have photographic memory.
Learning a quote, fact or language is easier when you know you will be using it often (and you have to tell your brain that you will be using it often by thinking about it constantly), but you must put a continuous effort to learn something in a spaced amount of time and not just ignore it.
I always believed that in order to be able to recall something in the future, you must learn that thing once (to open your mind to it) and then learn it twice (to imprint it in your brain, specifically at a later time when the “familiar” sensation hits). A third time isn’t at all bad, but welcomed as a form of “refreshing”.
This isn’t the same as school “cramming” when you memorize everything in one hit and then expect it to forget it after. This is actual learning, something you can pull up at any moment in the future, but it must be something you are open to at all times, not just when you have exams next week.