If you look at the list of poisonous mushrooms and compare them to a list of all mushroom species there are not very many of them.
If you look at a list of known edible mushrooms there are not a whole lot of them either.
There is an awful lot of mushrooms which are regarded as inedible or unknown edibility because they are to tough, to slimy, to small or taste horrible.
So the thing is to learn which ones are worth bothering with and concentrate on them.
You might want to be aware of the most dangerous ones so you can avoid them, but if you follow the don't eat unknown stuff rule you are OK picking stuff you know to be good.

I would like to add that if you compare poisonous to safe species the mushrooms are a safer kingdom than the green plants are.
The number of poisonous plants in relation to safe plants is much higher than it is with the mushrooms, and some of them are poisonous in much more interesting ways.

Edit: I think Dweste is pointing out that you should get some education about them so you can use them safely.