It's easy to be good to people when they're being good to us.
It's easy to show mercy when they deserve it, they were merciful to us

Does it make any difference ?

The real test is when they've betrayed you and now they need your help.
When they pushed you down and now you have the power to promote them.
When they've been rude to you and now they're asking for a favour.

Are you going to treat them the way they treated you ?