Sure there are happy relationships. I'm in one.
We do it by respecting each other, by treating each other like friends. Because we
are friends. We do not go out of our way to hurt one another. We do our best to be kind, and to take an interest in (or at least a neutral position towards) things and people that are important to the other person.
We trust each other because we do trustworthy things. I don't know how else to describe that. We just don't screw with things needlessly, if that statement makes sense. We expect to trust one another. We do our best not to let the other person down. Honest and love come from these things, too.
He is the most important person to me. Ever.