I had started a moderately successful company during dot com 1.0 when I was still in high school, my biggest issue was dealing with the downs, the rejection, the "no" from customers. One thing I found amazingly beneficial was to become a car salesman for a while. It's one of the toughest type of sales there is, everyone just hates you(even your co-workers/managers) and even good car salesmen will only sell a car to about 1 in 5 people they talk to, and on a weekend you might talk with 10-15+ people.
This obviously isn't a solution that'll work for everyone, but if you had just a year early in life to spend on a car dealership selling cars it'd be an amazing experience for learning. Now when I hear a no, or experience failure it just doesn't even phase me, I've already heard no tens of thousands of times. I'm sure there are other types of sales where this could be learned, but if you want to be a founder I sure think there'd be a huge amount of benefit gained from a car sales type experience.
Something along these lines - one piece of life advice I often hear is that everyone should work in retail/sales for a bit, just to get a taste of rejection and learn to deal with it.
This obviously isn't a solution that'll work for everyone, but if you had just a year early in life to spend on a car dealership selling cars it'd be an amazing experience for learning. Now when I hear a no, or experience failure it just doesn't even phase me, I've already heard no tens of thousands of times. I'm sure there are other types of sales where this could be learned, but if you want to be a founder I sure think there'd be a huge amount of benefit gained from a car sales type experience.