What's "a blessing and a curse" mean? When can this expression be used?

Native speaker’s answer
Rebecca
If something is a "blessing and a curse," it means it is a good thing and a bad thing at the same time. It has positive and negative sides to it for different reasons. You can use it when you want to express that something has positive and negative effects. Ex: Visiting my parents for the weekend is a blessing a curse. It means I get to have homemade food, but it also means I don't have much privacy. Ex: Money is a blessing and a curse. It can help you live well, but it can also tempt you to make poor choices.