They lean on each other
Happy couples come to each other for comfort, for support and for counsel. They respect each other's opinion, and trust that they are being heard. These couples know that whatever they're going through, their partner will understand. Or at least try to.
There's no pride in these relationships. They know that they can't handle everything on their own, so they don't even try. They share, they discuss, they ask and they listen. They support.
If she is having work problems, he's there to defend her thought process and help her with tomorrow's battle. If he's in a weird family argument, she's there to navigate the mess and to offer help in seeing the bigger picture. If she has a really tough decision in front of her, he's there analyzing the pros and cons with her, while still encouraging her to trust her judgment. And you know if he's in the wrong, she's definitely on his side, challenging and listening the whole way through.
They're partners, they're advocates and they're friends. No matter what.