In many ways, learning a language is like learning to play a musical instrument such as the piano or guitar. You are learning several things all at once, a new vocabulary analogous to musical notes, a new grammar analogous to music theory, and a new culture analogous to music history.
Piano learners are often frustrated because they feel they are not ready to move on to the next harder lesson or to play the next harder song. They want to master last week’s lesson before progressing to a harder lesson.
Good professional music teachers however teach according to a completely different schedule. A new lesson is delivered even before the learner has mastered the last one, and new songs are assigned which are just a little harder than the learner is technically ready for. Surprisingly, after a few weeks of progressively harder lessons, the learner can play the earlier, supposedly hard songs better than if they had attempted to perfect them in the intervening time.
Although it may sound like black magic, the phenomenon is actually quite well known in the creative industries—music, fine art, motion pictures, writing, etc. It works because of the following.
Your brain needs time to assimilate the new knowledge, commit new muscle memory, etc. Assimilation is an organic subconscious process that takes time to take root. During this phase, you may not observe any progress no matter how hard you practice. Moving on to the next harder song somehow helps you assimilate the current yet-to-be-mastered song.
Staying at the same level for too long can stagnate the learning process. Without observable signs of progress during the assimilation phase, the danger of quitting altogether is very high. Moving forward creates momentum to get you to the next level.
Language learning is analogous to learning to play a musical instrument. Internalizing the new language takes time. When progress seems stalled, the temptation is to try harder to get something down pat, e.g., trying to memorize the conjugation table of the omnipresent verb ‘ir’. Boredom and frustration soon takes over, and eventually language learning gives way to something else more fun or ‘with higher priority’.
The key is not to get stuck. Even if you have not mastered some grammar rule or memorized some words, learn something new and potentially more advanced about the Spanish language. What seems hard to you right now will become easier later. If it takes 10 (a totally arbitrary number) exposures to a word or concept before it is assimilated, so be it.