Dale Carnegie

When we hate our enemies, we are giving them power over us: power over our sleep, our appetites, our blood pressure, our health, and our happiness.

Our thoughts make us what we are.

...the best possible way to prepare for tomorrow is to concentrate with all your intelligence, all your enthusiasm, on doing today's work superbly today. That is the only possible way you can prepare for the future.

Flattery is telling the other person precisely what he thinks about himself.