Have 3 glasses of water, one hot, second warm and third one cold. Dip your one finger in hot water and one in cold water. After 2 mins, take out your fingers and dip them in warm water.
Finger dipped in cold water will find the water hot, and finger dipped in hot water will find the water cold.
You will say, this is obvious. Our body temperature tells us if the other thing is cold or hot.
Then why is it not obvious to us, that it is our state of mind which find the world around us good or bad. We judge people and world around us not based on what they really are, but we judge it based on our state of mind. Stop judging and you may find everyone warm towards you.