Ok so I've been playing for about a decade, but only starting GMing about 3 years ago. So far I've GM'd 1.5 campaigns.
The good:
-players are having fun, both with the rules and the story
-I'm having fun, especially with the story
However, the players are all longtime veterans with much more experience than me. I have a tendency to throw higher CR situations at them, and they often handle them deftly. However, there have been a few occasions where I had to "roll behind the screen" when someone is close to death, indeed, someone would have died twice if I had not played god. The players are unaware of this, but my question is, am I doing something wrong?