Life moves quickly. Although it would be a wonderful thing to be able to "prove" what you have done to others, we simply do not have time. The Universe gives us opportunities to be kind to others, kind to animals, kind to the Earth, and kind to ourselves, every day.
We may or may not know what kindness is. Kindness comes from the heart and can be both learned and intuitive. Some of us may not even know when a kindness is done to us/for us. We are stretched to let go of our belief systems, to act with compassion.
We do not know how to live life. The Angels say that it is simply a matter of letting go of over thinking a situation. By letting go, and feeling love, we can all act with the greatest and highest good guiding us.