Free will is the nature of how everything you decide, do, and feel comes to pass.
You are not destined to cry when your ice cream falls off the cone. it is your decision to react.
Even if your entire life was spent on a rail. Your free will is your nature. Even deciding that destiny and fate is pushing you this way or that on its opposition you are deciding for or against your "alleged" destiny.
Destiny is the nature of the unknown. The only thing you are fully committed to is never knowing the future. To indulge there is an order of events or something beyond this unknown is an indulgence of the ego. Your mind cannot fathom destiny but as an scape goat over the use of your free will.
Free will is the nature of the equation destiny is just the X of it that you cannot factor or fathom.
