What do you think of me being 100% honest with my boyfriend?
Why do you want to be 100% honest with him?
I want him to know I'm a true friend.
That's good, honesty is important in a relationship. If you lied to him he would lose trust in you.
Yeah, well, my boyfriend was an idiot and just left me for someone else because of my honesty!
That is actually a good thing, because if he couldn't handle your honesty then that means you two weren't meant for one another. You wouldn't want to be in a relationship where you're expected to lie all the time, would you?