The next item on the list brings plenty of the first, and they're closer to you than think.
In the current world climate, this single complication of adulthood plagues you with worry almost as soon as you hit puberty, since your body is already capable of making them by then. Once made, they can worry you from the time they start growing in a female anatomy (or from the Stork starts cooking them, depending on what story your parents told you about how they are formed) until well after they walk, talk and do adult things just like you grew up to do and sometimes well past when you're no longer around or able to provide.
They are the source of many adulthood risks (bills and grey hairs included) and the suction devices on a lot of allowance.
In short, these (at first) tiny adorable humans are the ultimate Cookie Monsters.