Hi gang got one for you.
Over the past few days, I have heard," what he/she doesnt know wont hurt them" from people.
What are your thoughts on this? I guess some things might be OK but were does it end?
What is OK to "keep" from your partner.
When is the trust line crossed?

Trust is crossed when you cheat. You shouldn't keep a lot from your partner its not good for the relationship

At my house, we have never opened each other's mail or listened in on each other's phone calls (or now cell phones and email). We do try to remember to tell each other where we are going if we leave the house, but that's just courtesy, especially if it will be a prolonged thing (dentist, doctor, visit to a friend) or if it's a trip to the grocery store and the trip-goer wants input from the other as to needed items. There are tons of personal things I have never told him, especially about old boyfriends, and the same for him to me. I couldn't care less about his old girlfriends. As you can see, we are pretty boring.