Never take anyone for granted, Karma will come for sure

The person you took for granted today, may turn out to be the person you need tomorrow. Be careful how you treat people.

Treat those who are good with goodness, and also treat those who are not good with goodness. Thus goodness is attained. Be honest to those who are honest, and be also honest to those who are not honest. Thus honesty is attained.― Lao Tzu

How we treat people is always our choice, and if we choose not to be respectful, it can come back to bite us. ― Alison Levine

How people treat you is their karma; how you react is yours. — Wayne W. Dyer 

No matter how cool, talented, educated or rich you think you are, how you treat people tells all. Integrity is everything.