Whatever has happened, whatever is happening and whatever will happen has already been decided. So, whatever one does or does not do is no longer a choice and hence, it is destiny.
Let’s say that the past, present and future information is written by a creator in a book called Predictions. But this book can never be accessed by anyone other the creator. Neither is the creator accessible to anyone.
In this case, there is a book which has all actions written. But, since the book is not accessible, no one other than the book’s creator knows about it. Hence, whatever one does, even thought already predicted, is not known and hence, it is free will.
At any point in time one can choose what to do or what not to do. This is completely up to the person and the circumstances at the time of action or inaction. Hence, it is free will.
Let’s say that all that one has done and one is doing is being written in a book called Predictions by a creator. But, neither the creator not the book is accessible to anyone. The creator also writes future actions and inaction into this book as this book has no bearing on anyone as it is anyways inaccessible.
As the book is always inaccessible, one can say that whatever one does or does not do is already predicted in the book. Hence, it is destiny.