It’s an association thing. For many of us, the only time we actually slow down is at bedtime. Our brain is used to us running around, processing multiple activities and generally being in an active state of doing. The minute we stop to rest, our brain assumes it’s time to take a nap.
Closing your eyes shuts out the light, which tells your brain it’s night time. A lack of light is known to have sleep-inducing effects on the brain. If you close your eyes to meditate, this physiological effect kicks in.
Meditation can be boring. There, I said it. Part of the reason why meditation can be challenging is that our mind craves the stimulation and distraction that it's accustomed to being surrounded by. When that’s no longer there, things can get pretty boring, particularly when you’re new to meditation. Have you ever fallen asleep during a dull lecture or while watching a bad TV show? Then you know sleep can be an effective escape from boredom.
Early morning meditation might feel more like sleep time. During my yoga teachertraining, we got up at 5:45 a.m. each morning to meditate. I repeatedly had to pull myself back from the brink of sleep. In my brain, it was definitely still night time and I’d barely woken up before I started meditating. It was much too easy to drift back off to sleep than maintain a state of alertness.
You might just be tired. Meditation forces us to confront how we’re actually feeling, rather than numbing ourselves to what’s going on. Sometimes we’re so busy we don’t even realize how tired we are until we stop. If stopping happens to be when you take time out to meditate, then to suddenly notice your sleepiness is entirely natural.