Even experienced people have things go awry. There's a guy I know on UER that fell through a floor in an abandoned courthouse. It was by no means, his first explore. At the time, the guy was a seasoned bridge climber. Shit happens.
Then there's the guy known as Captain Aquafucked...
I'm NOT going to say his name, but this is the story:
In Van Courtland Park in The Bronx, NY; there's a waste weir that was part of the Old Croton Aqueduct. It is possible at various places to actually get inside the aqueduct and walk through it. There were no pumps in the aqueduct. It was all gravity and siphons.
In an attempt to gain access to the aqueduct, the explorer in question tried to get in the aqueduct via the weir in Van Courtland Park pictured below:
There is a doorway, but it has been sealed with cement blocks although there is a large hole in the roof. The explorer in question, using a rope, scaled the side of the weir and then rappelled into the weir via the hole in the roof.
He landed a little hard and twisted his ankle and discovers he can't walk, never mind climb back out. He also finds that he doesn't have very good cell service and can't make a phone call, but he does manage to get a text message out to another area explorer in the area. That person then assembled a rescue squad to go out to the weir and extricate him from the weir.
It took a heroic effort to get him out, but they did succeed. They got him to a hospital for medical care and mission accomplished.
In any case...
If you're not comfortable with something, by all means avoid it. This isn't the army. There are no rewards for heroics, although they do make for good stories.