Current understanding of the process of therapy and development focuses on the interactions between the partners. The interaction is a negotiation of differences and of change. The equilibrium of the relationship is inevitably subject to frequent destabilizations, by virtue of normal developmental processes, life events such as losses, and the divergence of aims as each process unfolds.

The destabilizations are pivotal to the creation of new states. If a newly emerging state is to be advantageous for the development of the infant or the health of the patient, the associated toxic affects have to be tolerated and dealt with openly. If the analyst defensively hides, opportunities for change will be lost and the old patterns will persist. The therapist and patient, like the parent and child, are engaged together in this mutually altering process.