Spanish personal A
Whenever the object of the action (the one receiving it) is a person or a pet, we must use the preposition a right after the verb:
Amo Madrid. VS Amo a María.
Odio la canción. VS Odio a Pedro.
Progress, Vol. 1
Progress, all volumes
Desirable difficulties
If studying feels effortless, you're probably not learning much. A bit of struggle during practice is a good sign. Difficulty isn't the enemy of learning; it's the mechanism.