Boundaries don't strengthen necessarily because feelings are integrated; strengthening boundaries is one of the prerequisites to feelings work. Weak boundaries contribute to the "taking on" of psychic energies around you, which compounds your own negativity resulting in excess negative feelings. That's why we always start all processing sessions with the invoking of the light, which is the traditional method of psychic protection and boundary affirmation. Working with the light over time will build your boundaries on the psychic level, which you will experience on a real life level with less interference/overwhelm/domination/manipulation from other sources.