After a child is first born, they are actually able to hear all sounds made by all languages, and that incessant babbling (you can tell I don't have kids) is actually something all babies do and reflect all the sounds of all languages in the world. These babbling sounds are made up of "phonemes", the simplest amount of sound. I've seen a few comments here poo-pooing this video as a waste of time and only a way to promote his business, but it actually reveals something interesting: all babies babble all the phonemes in the world, and they do it in the same order, which is remarkable. A baby in China babbles in the same pattern that an American child babbles.
Once the child begins to hear the words of their parents mother tongue, they begin to lose the phonemes of other languages. So much so, that they (and adults too), can't even hear other phonemes. For instance, a Japanese-native speaker can't pronounce the letter "L". It comes out as an "R" sound. However, if that same person was grown up in an American family, they would be able to speak that "L" sound.
So back to your Spanish learning, there may be some sounds in the language that you can't possibly hear or say, because the phonemes of the language were "removed" from your comprehension way back when you were a child.
I believe I have that all correctly. I haven't got back the results from my midterm that I just had the other day, and I may have crashed and burned this comment.