I went off fungal foraging when I was shown a yellow staining mushroom by an expert. It looked like a mushroom, it smelled like a mushroom, it didn't grow in the same environment as a mushroom, but the key to not eating it (it having nasty effects) was to spot the yellow stain at the base of the stipe, and I couldn't see it at all.
Further confirmation of the necessity of avoiding non-normal mushrooms was when my niece gave me a kit for oyster mushrooms. Lovely they were. It turns out a few people have reactions to oyster mushrooms. I am one of them. Projectile....you don't want to know.