"I went on a weekend trip and didn't invite friend A, so I hope friend B keeps it a secret and doesn't tell anyone I was there" is the kind of social dynamic that people grow out of in high school. If you are having trouble with it as an adult then it isn't really Instagram's fault. People talk to each other and share stuff, and sometimes they talk about you, both online and offline. Just live your life without being…
I've tried to incorporate the notion that it's none of my business what other people think of me. I don't always get it right, but having that attitude has helped tremendously on reducing my cortisol levels.
Having a good thing happen or preventing bad things from happening sadly show up as high stakes butterfly effects of the perverted social ranking and opinion games.