We learn from the past so we don't make the same mistakes in the future. Plus it's important to know the past because don't you want to know what happened before you existed rather than being an ignorant fool? We do worry about the future but there isn't much you can do because it hasn't happened yet and it's unpredictable. You can't waste time worrying about the uknowns so much but you can learn from the past to be a more well-rounded person that can be better prepared for the future, whatever should happen.
Edit: Dangit Alex you beat me