When I say "awaken your heart," I mean that you're willing not to cover over the most tender part of yourself. Trungpa Rinpoche often talked about the fact that we all have a soft spot and that negativity and resentment and all those things occur because we're trying to cover over our soft spot. That's very positive logic: it's because you are tender and deeply touched that you do all this shielding. It's because you're soft and have some kind of warm heart, an open quality, to begin with that you even start shielding.
Excerpted from: The Wisdom of No Escape And the Path of Loving-Kindness by Pema Chödrön, page 62