What is the story The Monkey's Paw trying to teach us?

the monkeys paw is a story about a monkey paw that can do magic.

Sergeant-Major Morris show the paw to Mr. White and his family . He tells him that the paw does magic to three separate men who could each have three wishes from it. That a old fakir put a spell on it because he was trying to show people that fate rules your life and those that who interfered get things back worse then it was before. Sergeant-Major Morris try burning it but Mr.white gets it before it does. After Sergeant-Major Morris leaves Mr. White, his wife, and son make a wish that they get two hundred pounds for pay the house. But nothing happen so they all go to bed. The next day the family have breakfast and joke about it is silly to think it has magic. So the son goes to work . Later a man come to the house to said that their son has die and gives them two hundred pounds like they wish for. After ten sad days past the wife think of a wish for their son to be alive again. So she makes her husband wish for that. They wait for a long time then they hear a knocking. The wife runs trying to open the door. Mr. White gets the monkey paw at the same time and wish for his son to be dead again. His wife open the door then lets out a wail he runs back to her. But nothing is there and the lights are on.