What is one aspect of someone’s life you think no one should have a say in?

This question needs to be reversed.

The default is that nobody has any say in anyone else’s life for anything unless it harms someone else.

Just like the concept freedom, everyone is free to do whatever they want so long as it doesn’t hinder someone else’s freedom to the same or cause significant disruption to how society operates.

Another exception is the concept of minor & guardian.