This technique can help you reset your inner state by gently shifting your attention to the area of your heart. You breathe slowly and evenly, then bring to mind a genuine feeling of appreciation, care or gratitude.
It is not about forcing yourself to think positively. It is about generating a positive feeling in the heart and allowing yourself to experience it. Time and time again.
With regular practice, this positive state can become more familiar and easier to access. Over time, the technique can help change your inner world not by denying what you feel, but by helping you choose what you want to generate next.
Practise only when it is safe to pause and turn your attention inward. Do not practise while driving, operating machinery or doing anything that requires your full attention.