What is the meaning of this quote. Yesterday is history. The future is a mystery. Today is a gift. That is why it is called the present?

A present, is not always a gift!

It means run your life, take chances, and you don't know what is going to happen tomorrow. Yesterday happened already so just do today and today is a gif.

Yesterday is history = The day before this is past, nothing can be done about it but to reflect.

The future is a mystery = No one can know what tomorrow will bring, so there is no reason to worry about it.

Today is a gift. = Take each day as it comes, for what it is. Use today to its fullest, there will be no other chance to do so.