The act of not just being nice, but showing sympathy and understanding (plus a lot more of kind acts). True kindness is often understood through true pain.
Former anti-socials and rejects have a better understanding of current anti-socials and rejects. Thus, it is hypothetically better if you leave the situation to the former to show kindness to the latter.
True happiness that is gained only through true pain.
Unless you've found the meaning of life, of course.
Being rejected many times by society, Rhea sought to reform herself; and after many trials and tests, she found true happiness.
Then she found the meaning of life.