I don't know if it is even possible to learn 'proper' attachments. Once the brain is developed it has developed... and the patterns of relationships we learn as children literally form part of our neural make up. That kind of stuff can't be 'done over'.
What we can change is our understanding of our patterns of relationships and modify our behaviors. But can we learn to attach properly, as in 'can we learn to form attachments like those who learned it in childhood'? I don't believe so... I think we can learn to do it 'better' than what we did before, but I doubt very much that we can learn to do it 'properly' (meaning in a fully healthy way).