Even after a good night sleep people can sometimes feel drowsy when practising mindfulness. Sometimes this is simply because you are deeply relaxed after some stress. As our nervous system is not used to our eyes being closed whilst deeply relaxed, unless we are asleep, our brain acts as if it is time to sleep.
Sometimes we feel drowsy because the room is too warm or too dark, or we practise with a full stomach. When drowsiness is overpowering, it is important to assess and modify the environment in which you are practising, such as increasing light intensity, decreasing room temperature, sitting in a less comfortable seat or modifying posture, keeping your neck and back straight with your knees below the level of your buttocks.
If you are still feeling drowsy, try to breathe slightly deeper for a minute or so, feeling the touch of the breath within the nostrils. If drowsiness persists, you can wake the brain by letting a small amount of light enter your eyes. Rather than fully opening your eyes, open your eyelids just enough to let you see the floor no further than about 2.5 metres away from your knees. If this is insufficient to counteract drowsiness, try practising while standing up for a few minutes. If this is still insufficient, go for a short walk and wet your face with cold water before coming back and continuing the practice.
Drowsiness too is impermanent!
Next: Poor Interoception