I've found respect and empathy to be significantly more important than happiness and positivity, especially because people's attitudes are going to vary as they go through different life phases. There's something to be said for limiting your intake of gloom and doom, but the friendships that last and provide long-term support are those that exist for deeper reasons than secondhand happiness.

I have two friendships that have lasted for over a decade now and one that's lasted for four years, and all were forged during difficult or uncertain times. One of them I was becoming close to as we both tried to keep away from unhealthy relationships, and my friend's ex was prone to emotional blackmail. But we had kindness and understanding for each other, and the respect to not abuse each other's support.

Those with good boundaries are also wary of "emotional vampires", people who search out those who are feeling better than they are in order to leech off of their good vibes and be validated by the acceptance of happier, stronger, more successful, or sympathetic people.