The jungle gym in the park is for climbing. A thrown rock can hurt someone very badly. A wound inflicted with a metal object is serious enough to allow chilul Shabbos to treat it. A car, traveling at even the slowest speed, is so big and heavy that it will hurt someone very badly. A person can drown in the shallowest water.
Firecrackers are so dangerous that they are illegal in many places.
Hashem wants you to take care of yourself. He wants you to do mitzvos with that body and soul. We know that Hashem protects all of us. He gives extra protection to His special tsaddikim. We still must protect ourselves.