Pay It Forward: Random acts of kindness really do make you feel happier and in control
This article quotes a couple of studies done by university professors regarding the effects of doing acts of kindness on the doer’s level of happiness. It also happens to cite Rabbi Greenbaum who began doing random acts of kindness to deal with his anger and grief when his wife was killed by the suicide bomber attach on Sbarros.

How Good Deeds Can Be Good for You! Helping others can help you to heal yourself, both psychologically and physically.
The Random Acts of Kindness Foundation

Cultivating Kindness: Tools for inspiring our kids to become givers
by Sarah Chana Radcliffe, M.Ed., C. Psych. Assoc.,
Aish.com

The Kindness of Strangers: Not everyone goes to their deathbed surrounded by loved ones
by Lauren Kessler
O, The Oprah Magazine