What once was mistaken is now forgotten and retold.To graphite, I am a loyal friend, I fix its slips and make amends.I shrink the more my help is sought, giving my form for your second thoughts. What am I?

I dangle from a scholar’s crown, then shift to mark the success you’ve found.

A jewelry for the wrist, I'm also there to assist. Shinning pretty in dangling light, This is will smile and delight.

It has three hundred sixty-eight wheels, one hundred eighty-four bars, and is three thousand three hundred thirty-three kilometers long.

Sometimes I come from a beating heart, sometimes from shadows after dark. Whether comfort or alarm I bring, what am I? Can you name this thing?