You should focus exclusively on whatever thoughts help make the mind firm so that it can give rise to goodness. Don’t dally with any other kinds of thinking, regardless of whether they seem more sophisticated or less. Shake them all off. Don’t bring them into the mind to think about. Keep the mind firmly set in a single preoccupation: That’s your true heart, the true heart of the Buddha’s teachings.
Ajaan Lee Dhammadharo