Someone always 'moves the cheese' -- and if the cheese is the reason you're in this game, you're at high risk of not finding it all worthwhile when you finally get there. You may be expecting a mouth-watering Maytag Blue and find a runny mess of Brie instead.
But please also realize that many other life paths experience this same phenomenon to some degree. The early years in most high-paying careers are full of paddle-paddle-paddle 80 hour work weeks for not a lot of money, with lots of BS and ethically-questionable tactics to put up with -- and of course, neither the time nor money to travel. Unless, as
@Promethean notes, you occasionally stick you head up out of the maze for a good look around.
You can enjoy medical school if you stick your head up every now and then. Appreciate the journey with some of the most intelligent and capable peers you will ever spend time with. Appreciate the challenge to your intellect, your creativity, your sheer stamina. Seek to learn and measure your success in knowledge gained, knowing that every other field falls far short in this regard.
And know also that life doesn't end at 30 or 40 or 50 or 60. The good times continue as long as your good attitude does --