It's true, being a surgeon is a life choice, not a job. It tends to swallow up a big chunk of who you are and what you do. There are folks who practice part time in a limited way, doing primarily breast surgery or outpatient procedures, like hernia repair, but that's unusual. I think that, to be a GOOD surgeon, you have to devote your life to it. Sort of like being a professional tennis player or golfer - it's just not possible to reach the level of expertise that you need unless you are living/breathing/pooping your pursuit. Certainly this is true during your training. You can count on 5+ years of being completely absorbed in your work, or you likely wouldn't survive. Most people who leave surgery during residency do so because of lifestyle issues.
The sacrifices that are demanded of surgeons really are so great that I don't think that the rewards are able to offset them, unless you are just pathologically, fanatically in love with doing surgery. At the end of a 36 hour shift, if the idea of taking a trauma GSW to the OR for exploration doesn't rally you to new levels of excitement, then you will be one the one-third of surgery residents who decide that it's all just not worth it. Being in the OR is the carrot on our stick. You either have that bizarre obsessive interest in it, or you don't. If you don't, I wouldn't put myself through the pain.