For some sleeping with night guards to stop teeth grinding is an unpleasant and sometimes painful experience.
Over the counter night guards are inexpensive and you can form them to your mouth by boiling hot water. I have used a few of these guards and they did not hurt when I formed them correctly. The first time I did not melt the plastic enough and this caused the painful gum problem I was having. Make sure you remelt the plastic and try again if this happens to you.
The next problem I have was spitting out the guard at night. Over time I would wake up without the guard in my mouth and it was somewhere in my bed. I ended up buying a professional night guard which was made by a dentist due to this. The guard cost me $450 which seems outrageous to me. It was little better than the cheap CVS night guard, but it was locked in my mouth. I no longer spit it out.
The next problem which I often hear about is that some guards cause people to gag. I have not had that problem, but someone emailed me with a solution of cutting the ends off of the guard so it did not go down your throat. The guard just needs to stop at the end where your molars are.