Learning English

Since I'm in a class devoted to learning Spanish, I've been thinking about how it was to learn English. It's almost the polar opposite of the way I've been learning Spanish. I remember having a list of vocabulary words that we were required to learn. We had to learn to spell, often by writing the words repeatedly. Grammar was an entirely different story. We had a whole class devoted to it until about forth grade, then the two merged. I used to love my grammar class, where I got to write poems about Freddy Kruger and ghost stories that were similar to what R.L. Stine was writing at the time. Spanish is completely different. There are no spelling words, no grammar, you are expected to learn how to hold a conversation quickly. How can I learn Spanish so quickly when it took me so long to "master" English?