I began to study English in school, didn't get much out of the lessons. In high school I began to listen to shortwave radio broadcasts by Radio Canada International, The Voice Of America, BBC World Service and other stations. It was a magical feeling itself to listen to someone talking through the half of the world, and it heated up my interest in English as well. And those programs were the only way I could listen to native English pronunciation (either American and British), and I tried hard to mimic the pronunciation.
Another big reason to learn English was playing computer games like Transport Tycoon Deluxe, SimCity etc.
Then lessons in the university. Didn't give much either by themselves, but encouraged me to write some essays which had somewhat improved my English skill.
Of course, the need to read programming languages documentation also contributed a lot. And English forums, and interest in listening to air traffic controller communications with pilots, and reading the last 3 books of The Wheel of Time series (because they hadn't been published in Russian) ... Those books, by the way, were so difficult to understand. When I made a decision to read them in original I thought that I have a decent skill in English and will have no problem understanding the texts, but the first few pages showed me that I greatly overestimated my skill. I pushed through anyway, looking at a dictionary for every other word :) and this was indeed a great exercise.
I learned from my learning experience that motivation is the main. You can learn pretty much anything to certain degree if you try hard enough.
So a lot of things motivated me to learns English. The main however was an irrational love to the language and how it sounds.
