Negative thinking, negative feelings come; positive thinking, positive feelings come. So, how should we think? Very simple; it is a learning process.
For me, if a thought comes and the mind gets agitated and suffers, I don’t believe this thought. Also, I don’t follow this thought, I don’t continue to think this thought; it is a wrong thought. Why? Because it causes the mind to suffer. But people don’t understand; they continue to think and suffer, suffer, suffer.
Why should I do it? Thinking and feelings are related. Because we don’t know the nature of the mind, we get tortured by the mind. We have a choice if we understand.