how can I keep my baked goods from going stale after they’re baked?

The short answer is keeping your baked goodies in air tight containers as soon as they’re cool. If you happen to be in a very dry environment, it can help to place a small piece of bread or slightly damp paper towel in the container with them to create a humid environment that will prevent staling. Nothing in the world will keep your cakes or cookies from eventually going stale, but a tightly sealed container helps give them a longer life.

But what causes staling?? Find the answer here.