See, that would require having good judgment and putting a thought or two towards contingency.
Nope. It would require a magic sixth sense that lets you know that the apparently trustworthy person you're with won't turn into a total asswipe six months from now. To date, there's no known method.
It also requires that none of his buddies will 'borrow' his cellphone when he's asleep/drunk and that he's incapable of hiding a cellphone in a place where you might be naked, or even just surprising you in the shower.
etc.
Short version: Life isn't the perfect little utopia you were imagining when you said that.