What if I fall asleep during a massage?

That is perfectly normal! (as it is to drool!)  Many people become relaxed enough to fall into a deep meditative or sleep-like state.  It is kind of like when you are driving down the highway on a familiar path and all of a sudden you realize you have gone 20 miles without even realizing how you got there.  If something negative were to happen in that time frame, your body would recognize it and bring you instantly aware so you could react.  Optimally, during a massage session, you will fall into this type of meditative state.  When you do, your body can devote more energy to the healing process.  Again, as an example, when you are sick, it is intuitive to sleep.  The more rest you get, the more quickly you may feel better.  Our bodies and brains are constantly doing a million different things.  When we quiet down our mind and body, we can divert the energy required to being awake to help bolster those processes that are key to healing.