So, because this question really is asked in interviews:
DO say something specific and personal about yourself, DONT say something generic like "I like the mix of humanism and science". For pete's sake, this is (hopefully) what you are going to do with the rest of your life. How does it apply to YOU? We could give a crap about generic philosophy.
What we want is a good mix in the class -and if you come across as this memorized cookbook of "how to get into medical school" we walk away having no idea of how you would fit into the mix.
It's ok to have a hodge podge of reasons, but you need to be coherent in your statement, and I'd really work on some "stream of consciousness" writing or journalling, and then go back to it a couple of days later and pull out the concepts you feel are most effective. Try to work on it when you are relaxed, and write for someone other than ADCOM, like your best friend -you can edit out the wildly inappropriate slang later.
A really good bit of advice I received was to NOT use NOT -that is, don't describe your decision via process of elimination (I didn't like my grad program, and started looking for something else to do.....), or to be negative in any way in your PS, other than a bit of self-deprecating humor. If you need to explain something negative, do it in the most positive way possible. Part of this is due to ADCOMs hypervigilance for applicants who will be unable to handle the pressure cooker -you need to demonstrate maturity, to show that you'll be able to buck up, even when you really are sick of studying and no longer remember why you didn't want to be a cowboy, a fire fighter, a bartender.....
Why I wanted to become an MD:
I played around with a lot of different ideas after teaching. The classroom made me realize I liked people and didn't want to live in academic research (mostly in a room by myself) for the rest of my life. I talked to a lot of people, tried different things, and figured out that the information and training I wanted was available primarily to MDs, so that's what I decided to do, once I figured out that it was possible for me to survive it (theoretically, there's a long way to go....but so far so good!). The MD is not some magical solution to my life. It is not the only thing I could ever do and be happy. But so far it's been a good mix of

and
😎, with the odd
😡 thrown in for good measure.
Hope that helped...
