In the past i have dated men who I knew I could only trust 10% not to sleep around, so I kept the relationship short term and casual, and felt no guilt about their tears when we parted.
My mother can be trusted, by anyone, literally anyone, 100% on money and property. But i know to only credit her with 30% when it comes to other people's emotional well being, and remembering that means I can still have a relatively pleasant relationship with her.
Everyone is various shades of grey. If you want someone in your life, figure out their shading, then trust them to be themselves.