All first responders I think, plus being a good parent is challenging and requires more guts than most jobs. Having patience to talk to your child and teach them even when you're tired and beat down from life is hard. Sleepless nights catch up to you.
A typical one is sales. Not salesclerk but the guy that goes out and knocks on doors - both corporate and residential. It looks easy but very few make it. If you DO make it, you make tons of money.