When a feeling or thought arises, your intention should not be to chase it away, even if by continuing to concentrate on the breath the feeling or thought passes naturally from the mind. The intention isn't to chase it away, hate it, worry about it, or be frightened by it. So what exactly should you be doing concerning such thoughts and feelings? Simply acknowledge their presence.
Thich Nhat Hanh, The Miracle of Mindfulness: An Introduction to the Practice of Meditation
mindfulness