From Rohan Healey's Greeks to Geeks: Practical Stoicism for the 21st Century:
"Fatalism, Determinism - Be It Gods Or Atoms
Epictetus: 'Remember that you are an actor in a drama, of such a kind as the author pleases to make it. If short, of a short one; if long, of a long one. If it is his pleasure you should act a poor man, a cripple, a governor, or a private person, see that you act it naturally. For this is your business, to act well the character assigned you; to choose it is another's.'
A big part of Stoicism is the idea that our path in life is pretty much mapped out, or at least that it might as well be considering that there will always be only one outcome to anything that we do or try, and we have no way of knowing how things would have turned out should you have tried something different. Now I'm not exactly sure if the Stoics really believed in a 'future is already planned out' fatalism, or if they were simply using what was the common belief at the time to communicate their message to people in a way that they would understand. Then there is the contradiction of when Epictetus or Marcus Aurelius will say that you have free will, indeed that it is all you have, and then later in the same passage talk about how we must accept our fate. This seems like a pretty big contradiction . . .
Determinism: Determinism is the view that every event has a cause and that everything in the universe is absolutely dependent on and governed by causal laws. Since determinists believe that all events, including human actions, are predetermined, determinism is typically thought to incompatible with free will. Basically, there are no coincidences, all is connected.
Determinism states that every event, including human cognition, behaviour, decision, and action, is causally determined by an unbroken chain of prior occurrences. Determinists believe the universe is fully governed by causal laws resulting in only one possible state at any point in time.
Fatalism: Fatalism is the belief that 'what will be will be,' since all past, present, and future events have already been predetermined . . .
Fatalism is seen as a submissive mental attitude resulting from acceptance of the doctrine that everything that happens is predetermined and inevitable. It is also a philosophical doctrine holding that all events are predetermined in advance for all time and human beings are powerless to change them.
Free Will: The theory of Free Will states that human beings have freedom of choice or self-determination; that is, given a situation, a person could have done other than what he did. Philosophers have argued that free will is incompatible with determinism.
Free will is the power to make free choices unconstrained by external agencies.
Indeterminism: The view that there are events that do not have any cause; many proponents of free will believe that acts of choice are capable of not being determined by any physiological or psychological cause.
Indeterminism is a philosophical position that maintains that any form of determinism is incorrect because it is ultimately metaphysical. Quantum physics has shown that not only is it possible for outcomes to be different, but even that millions of alternate realities are playing out all at the same time in different dimensions or spaces.
So these are the most common fields of thought on this subject, all seem contradictory except for one thing they all have in common. The single consistency between these theories is that no matter which you believe, only one thing can actually happen to you at any given time, life is linear, we can't go back and see what would have happened if we had made a different choice.
. . . [W]e still have only one reality to deal with, and no matter how you look at it we have to accept what comes to us. Once something has happened it's already too late, it's time to move into acceptance and making the most of what is put before us. However, in the present moment we do have thoughts, opinions, and beliefs that are fully within our control (or at least seem to be), that we can change as we please, and when you consider that it is these exact opinions and beliefs which shape how we feel about our uncontrollable circumstances we're not doing too bad.
. . . As Epictetus says: 'Don't demand that things happen as you wish, but wish that they happen as they do happen, and you will go on well'."