It's a rational fear, but it ain't necessarily so that glass toys will hurt. A few points to keep you from discomfort...
Start slowly (good advice with any toy or real life 'hardware'
). I'm assuming you already have toys in more flexible materials (eg silicone)? Select your glass toy a size smaller than what you're already comfortable with. Because glass is harder, it seems
bigger than it actually is. I find subtracting about 1/4" in diameter from your favorite size in a flexible toy material is about right.
Of course, use plenty of lube and be patient. Insert gradually. Go slow until you're comfortable. Just as with most other toys, once it's fully inserted and comfortable, you're pretty much good to go.
My wife and I have a number of glass toys. We have a beautiful glass strap-on that my wife pegs me with from time to time. I use glass butt plugs almost always when I'm getting warmed up for pegging. I have a short (2" plug that's about 1.25" diameter which is the perfect warmup for an average dildo (eg the Vixskin Mustang, which is 1.5" diameter) and the Cobalt Bubble Plug
to warmup for medium/large dildos (such as the Vixskin Johnny). I also use both of those plugs fairly often for anal stimulation in solo play.
And yes, they are all quite comfortable! The Cobalt Bubble was a wee bit uncomfortable the first time I used it, but that was because I underestimated how big a 1.625" diameter glass plug would feel. The next time, I used the small plug (which goes in almost effortlessly) first. After that, inserting the larger plug was easy. And comfortable.
Glass holds temperatures better than other toy materials. If you heat or cool it before play, it will keep the heat or cold for a long time during play. Which can be a lot of fun! Glass is also REALLY easy to care for, completely odorless and although it may sound fragile, a well-made glass toy can last a lifetime (or longer) if you take care not to drop it from 3 stories onto the sidewalk or anything like that!
A few years ago, glass toys were fairly rare and usually expensive. Now, there's a lot more variety and prices are a lot lower. Considering the durability, glass toys are possibly the most economical choice in the long run. Have fun!