This is a query that has been raised by more than one newcomer to astral projection, so I thought I would address it in a blog post. The answer is surprisingly optimistic:
As long as nothing physically happens to your body whilst you are “out,” this is guaranteed never to happen!
The fact is that there is no evidence whatsoever that getting trapped outside your physical body whilst astrally projecting has ever occurred, nor that anyone has died as a result thereof. And before you say, “well there wouldn’t be,” there isn’t any evidence of known astral projectors mysteriously dying for no apparent reason either, which is what you would expect if this phenomena occurred.
The only conceivable way that you could get trapped outside your body whilst astrally projecting, is if your physical body died in the meanwhile. And then, being trapped outside your body is the least of your problems!
So in other words, the simplest way to avoid this is the same way you would avoid dying generally – live a healthy lifestyle, and avoid doing anything unhealthy or dangerous.