I will give you two stories (both mine).

It was 1999 and I was 15 years old. My mom's friend ask me to deliver some christmas cards. The reason was that there was a monopoly of mail delivery in my country and it was so expensive that it was worth it to pay a young kid to do it. I did it for her and then for another, then another, and again. I realized that the monopoly actually created an opportunity. It just shocked me how happy people were to actually pay half the price and don't have to deal with a government office!

I reached out to the dad of one of my friends and ask him if I could deliver his flyers (he had an insurance company). Half the price. Short story, I hired 20 of my friends and we build a company around it.

Second story.
I was a partner in a consulting firm and I was making good money. Like really good. But I was always fighting with my partners because we had a different long term vision. I woke up one day and say "this is it, I'm done". I realized I didn't want to go to work anymore no matter how much money I did. I figured out that I would find something else to do.

If you want to know more in detail please give me a call. Some of this moments are very personal. I would like to share them but not that openly with everyone :)