"I'm suspicious of people who don't like dogs, but I trust a dog when it doesn't like a person. “ - Bill Murray. This is a funny quote, but there is truth to it. It's almost a comedic take on the Philosopher Diogenes of Sinope

"I fawn on those who give me anything, I yelp at those who refuse, and I set my teeth in rascals."[20] Diogenes believed human beings live artificially and hypocritically and would do well to study the dog. Besides performing natural body functions in public with ease, a dog will eat anything, and make no fuss about where to sleep. Dogs live in the present without anxiety, and have no use for the pretensions of abstract philosophy. In addition to these virtues, dogs are thought to know instinctively who is friend and who is foe.[54] Unlike human beings who either dupe others or are duped, dogs will give an honest bark at the truth

I think the only sane approach is to just assume someone is going to break your trust, someone that you care about, it's only a matter of degree. If you want to remain a social creature you just have to develop thick skinned, decide what you can live with and what you can't in terms of others flaws. Is the person who broke your trust is a flawed friend or an enemy is the ultimate question, and if you decide they are a flawed friend, then forgive them and move on.