Magic WAS my high school years. My god, I never stopped playing that game. If I couldn't buy the cards, I would make proxys just to test the deck types. If no one was around, I would goldfish a deck (Play a single player game basically, to see how quickly I could attack and cast spells for 20 points of damage, ) or play both sides of a match and evaluate potential strategies between different designs. I had a folder dedicated to a variety of design ideas, and I read all my copies of duelist, wringing every last little bit of data from it I could, bookmarking the pages with pertinent graphs. Hell, whenever I got money, I generally evaluated that money by dividing the dollar amount by 3, trying to figure out how many booster packs I could get. If there were the online sites where you can buy any card individually, I would be living in a gutter today.
These days, I'm not so obsessed. I more of less pool my cards with some friends, and every once in a while I will buy a new preconstructed deck to mess around with, or buy a few singles to make a deck that looks like fun. Then we will play a big multiplayer game once a week or so, and occasionally do a quick match. Still a ton of fun, and a lot more realistic now that I have real bills to pay.