I learned not to loan out money in high school. Kids always told me that they'd pay me back and a week or 2 weeks would go by and all I'd get was "sorry, I'll pay you back sometime." and they'd never deliver. After 3 people that I was supposedly friends with, I decided that I don't do money loans. If my "friends" want money, they can go get a part time job and make their own.
I learned to quit trusting my ex wife during my divorce after some of the things she said, lied, and did. After 11 years, the person I trusted with my very being was now a liar and a cheat. A woman changed for the worse. We have joint custody, it's week on, week off. But now I have them full time. She'd make promises to the kids on her weeks and then bring them back to me 2 hours later when it wasn't my turn just because her current boyfriend, and she changed boyfriends a lot, wanted to go on a date. The kids would be upset, asking "but....but.....I thought we were going to go out and eat."
If I didn't take my kids. She'd leave them alone for who knows how long. Once my daughter told me that she left her and her brother alone for 2 days on her week and lied to me and said that she had a friend watching them.