[jsnyder]

Within the practice of Shamatha a training method developing a mind that holds steady on its object of concentration there are two types of "sinking".

The first of these is called "gross sinking", which happens when your mind/body actually fall asleep. This is generally to be avoided, because it can easily become a habit and it wastes your meditation time and devalues your good intention to spend time meditating. There are several fixes for this problem. First, if you close your eyes during meditation, you are encouraged to open them, at least partly. If your mind runs away too much with visual phenomena, then open your eyes towards a blank wall, or close your eyes, but face a strong light source/window.

Other postural fixes for gross sinking that I involve changing you meditation pose. If you sit in a chair, make sure you don't lean against the backrest. If you need a chair because floor postures are uncomfortable, try sitting on a swiss exercize ball, these will keep your posture upright and alert.

If you sit on a floor cushion I have discovered what are often called portable/travel cushions, these are a cover over an inflated (basket ball sized) bladder. These are very stable and comfortable when you are alert, but will wake you with a start if you drift off.

Finally, try meditating while standing or walking. I prefer standing because I do like to mostly close my eyes but many vipasshiona meditation halls have an indoor or outdoor track that you walk back and forth on to meditate.

These various techniques can be used to get you past the gross sinking phase. The second type of sinking is called subtle sinking and it occurs when your concentration while unbroken becomes soft and indistinct. The analogy is visual fogginess, in the same way your mental clarity, your moment-by-moment presence dulls a little though it doesn't run away altogether. Good luck with your practice