Cyanides are not just something in a little vial that makes spies' mouths foaming. They are a common and sometimes very important part of nature and our lives!
What you should remember about cyanides is that they are acutely toxic. That means that if cyanides get into your body and you survive, the cyanide will eventually completely leave the body. It doesn't build up over time. And the similar principle applies in nature as well.