I'm reasonably certain my wife won't poison the milk in the fridge and she's reasonably certain I'm not going to read her emails. This is only a safe bet until

I'm reasonably certain my wife won't poison the milk in the fridge and she's reasonably certain I'm not going to read her emails. This is only a safe bet until it isn't. If she starts asking about your life insurance and hiding her phone from your view, you will know it isn't a safe bet anymore.