pay it forward

To perform some act of kindness for someone else after being the recipient of such an act oneself. Treat people with generosity and kindness. Chances are, they'll pay it forward and be kind to others, too. Having a kind, caring academic advisor made my transition to college life so much easier. Now that I'm a professor, I try to pay it forward by carrying myself in the same way whenever I have the chance to mentor a student.