Why was George Washington's relationship with his mother strained?

George Washington wasn't close with his mother(Mary Washington) at all. Mary Washington was a bossy women with a cold expression. She was never proud of her son even after George became president, or became a very respected general. Even George's friends were very scared of his mother. So, George started his letters to Mary as " Honered Madam " instead of " Dear mother ". Also, George never introduced his wife( Martha custis) to his mother. They didn't get along that well.