This is a great question that most ask themselves before committing to a demanding career. As a medical student, I can tell you that the best way to figure out if medicine is for you is to volunteer in a hospital, work in in a doctors office, and shadow doctors. You want to see if the lifestyle and responsibilities of being a physician is for you. Overall, being a doctor is an amazing, challenging, and honorable. I believe it is truly amazing to give patients what you can with your knowledge and experience, but the road there is not easy.
Is the training of 8+ years worth it? is it exciting? would you love to learn for the rest of your life? Do you enjoy solving health/medical/scientific problems with you many years of education? can you handle working with, and helping, many different types of peoples from different cultures and upbringings? can you handle seeing and dealing with death or extremely sensitive issues? You are not just helping people as a physician, you are responsible for their lives and well being.
I knew medicine was for me after I finished my bachelors degree. I took two gap years and worked full time a research coordinator, volunteered in a hospital, and volunteered in a mobile clinic. I got experience in private practice and hospital setting, working with patients from extremely impoverished to wealthy, and from healthy to dying. I saw medicine from as many angles as could before committing. Even though I was working 40+ hours a week, I still enjoyed what I did. You don't need this much time and experience to figure out if medicine is for you, but you definitely need to get your feet wet before deciding. Not only is the process of getting into school challenging, being a student is challenging and the entire process of becoming a physician is expensive (tuition, cost of living, books, board exams, etc). I will be in over $300,000 of debt when I graduate. You want to do all that you can to make sure that becoming a physician is the right choice for you and you cant see yourself spending your one beautiful lifetime doing anything else!