Speaking as a sometimes-introvert, it's very, very easy to go travelling and not meet anyone.
My record is three weeks on the road with no conversation deeper than ordering a meal or checking in to a hotel. And I'm not really all that introverted.
I did then use gumtree to find some folks to travel with, but still, just saying 'travel' is not really a cure-all for introversion.
To throw my anecdote out there, I find that I have no trouble at all talking to people on the road and making friends but I can't do that at all when I'm at home. I have very few friends at home but when I'm out traveling I find myself opening up conversations with perfect strangers. I've made some terrific friends doing that.
Just wish I could make myself do it at home, too.
I also can't imagine someone who is an extreme introvert would be able to pick up odd cash jobs really easily, and also don't seem like great ways to have extended contact with other people.
It's an interesting point that risk makes you feel alive, I've experienced it myself and you feel brilliant afterwards.
Once I got trapped in a wave machine as a child and was being spun around underwater, but kept down the panic and managed to work out how to get out again. I was probably underwater for a total of 90-120 seconds. People were going crazy when I came back up but once I'd got my breath back I felt incredible.
I wonder if it's possible to apply this sort of risk-reward feeling to earning money? Is this what people feel like when they put everything into a startup? Money just sort of seems so mundane when compared to physical activity.