No go around, no throttle, and only mother nature for lift... your hobby is what I would consider an emergency... so how safe is it really? How often can you not make it to the runway, and of those times how often does the plane end up damaged or the pilot end up hurt/dead?
I think that, depending on terrain, land-out is not all that hazardous: your stall speed is fairly low. Of course, Glider Bob died by crashing a Stemme into Colorado woods in a thunderstorm, so it's possible to get seriously injured in a glider. But as long as you aren't pushing it that hard, you'll be fine.
However, there are some things you must be vigilant about. The tow preparation must never be lax: check your ropes, make up the full plan, including the direction of turn above X (usually 300') and the point at which you decide on attempting the downwind. If the rope breaks, you'll have to maneuver instantly and you won't have the time for confused, indecisive action.
If you run off a winch, you have to familiarize yourself with a set of specific hazards, and internalize the canned reactions to them. Again, there won't be a time to refer to a checklist. It's the price for the nearest thrill to a cat shot that a civilian can experience.
Overall though, I'm quite amazed at the stunts people do in gliders and then walk away, simply because the energy at the impact is lower. I saw videos of people lawn-darting it in and walking away. In a Cessna that you kill them almost certainly.
