To be close to the truth, we need to be able to put ourselves in others' shoes, by looking objectively from a different perspective, and by changing your position to look from different angles. We need to be able to question ourselves and be less scared to be wrong. If we are right, be proud of it; if you are wrong, own it!
Indeed if we look for things to be grateful, we will find plenty of them around us. If we are constantly unhappy and sad, we will find that the grass is greener only on the other side.