Some people are attracted to medicine because of the prestige a career as a physician carries, even in today's world. Other people are attracted by the challenges posed by one of the most difficult professional career tracts. Others are just stimulated intellectually by it while others think of it more as an art form. Some (much more than many here are willing to admit) think about all the money they can earn as doctors. Contrary to what many here state not everyone in the US can easily earn at least $100,000 or go into investment banking. For a select few medicine is a calling, they were born to be doctors and knew it since they could remember. Others are pretty much groomed to be doctors since they were very young, or worse, forced into medicine by selfish parent who want to achieve frustrated dreams vicariously through their children.
For others well, medicine wasn't really in their plans at all, they just kind of stumble upon medicine as a likely career choice a bit later than others and decide that may just be a great and fulfilling career choice for them (as happened to me).
How do you know its right for you? Only you can know for sure. Just try to find out as much information as you can. If at all possible ask a local doctor if you can shadow him for a day or two to get an idea of what medicine is really like and if it's for you.
Take each advice with a grain of salt as it is mostly subjective opinions that might or might not apply to you (including my post). Also when going into forums such as these understand that there is A LOT of BS going on around here. Not everyone here has a 30 MCAT or above, gave up a lucrative job in investment banking to earn "less" in medicine because of their "love" and "compassion".
Medicine in a great and rewarding career and after three years in med school I have to say I made the right choice
for me. You have to understand that while it can be very rewarding profession the road to get there is longer and more difficult than most any other profession. If money is what motivates you (contrary to what many here say, it is NOT a dirty word) then understand that many, many difficult and long years will pass before you see any real money.
I apologise for my rambling, but after 26hours on call in theOR I don't care much for my "perfect" writing. I just hope I made your choice that much clearer.