Kindness is a necessary addition to everything.
All the best qualities of mankind are meaningless and worthless without kindness, and even the worst vices can be easily forgiven with kindness.
There is a natural kindness which comes from our external attributes, from our inheritance, audience, good or bad indigestion, success, etc. This kind of kindness is very pleasant, both for the person who experiences it and for the people around him. And there is another type kindness which comes from inner, spiritual work. This kindness is less attractive, but although the first kindness can easily change or be transformed into hatred, the second kind of kindness will never disappear and will constantly grow.
The goodness which you do gives you pleasure, but not satisfaction. No matter how much goodness you do, you should wish to do more and more.
Kindness is the major quality of the soul. If a person is not kind, it is because he was subjected to some lie, passion, or temptation which violated his natural state.