The 'Fate versus Free Will' argument has run not only throughout the history of Astrology but the history of philosophy and indeed the history of mankind, so I doubt we're going to solve it here
Dave gave a personal view, so will I. Firstly it depends on what we understand by the terms 'Fate' and 'Free Will'. Does Fate mean that every single event is predetermined and for humans that every act or thought is predetermined. I remember a reference to a Greeek philosopher in one of my philosophy classes who believed in predetermination. Allegedly one of his slaves ran away but was caught. When the philosopher got him back he announced that he was going to whip him. The slave responded by saying 'Master it was not my fault, it was determined by Fate that I would run away, I had no choice'. To which the philosopher agreed but the said 'But Fate also determined I would whip you for running away'.
Now that's an extreme view of the Fate argument. In reality most fatalists will allow some degree of choice available to humans, but that degree is small and is likely not to affect the outcome very significantly. Some Stoics believed that the choice lay in accepting Fate and learning from it, or resisting it.
Now to what extent do I have Free Will? If I choose to fly or to live for ever or to run a mile in 30 seconds, there's no way that I can put my 'Will' into effect. There are external physical limits to my ability to act and to do what I intend to do. In reality the most I can do is push the boundaries of the physical world, and indeed the social world and perhaps change the course of events. We're looking at where we believe the balance lies between my ability to affect the world (or indeed universe) around me or to have to give way to it.
It's not necessary to believe that the external environment is totally determined, Heisenberg showed that there's some randomness to it. As does Chaos theory. Yet faced with a Tsunami, there's nothing I can do, no matter how much I will it. Faced with something that is more easily swayed, then I can indeed influence the outcome.
Astrology has been criticised, both in the traditional period and in the present day for forecasting the future. If the future can be forecast, so the argument goes, then the universe and the people within it must be the subject of Fate - what will be will be. Both Dave and I have argued that a forecast is based on the assumption that things will stay the same, but if the subject chooses to (and is able to) they can forestall the forthcoming forecast event. It's the same situation as if the doctor tells you that if you don't lose weight you are likely to have a heart attack. If you choose to follow her advice then the heart attack might well never happen.
Both the doctor and the Astrologer base their arguments on a stochastic view of the world. That is that the event is not predetermined but that it is probable, to a greater or lesser degree. The actions of the subject in one direction may help to increase the probability but actions in another direction may reduce it significantly.
At the time of the Hellenistic period in Astrology, most Astrologers, were influenced by the dominant philosophical view, stoicism, and that was largely fatalistically inclined. However as David points out that did not hold for all of them and there's something of a continuum of belief. But modern psychological astrologers can be just as dogmatic - I've seen people coming to this forum who have been told in no uncertain terms that something bad will befall them and there's nothing they can do about it. I've even seen an argument that a mother was 'fated' to kill her daughter because of particular aspects between their charts.
That in turn could lead to a discussion about what the chart actually shows - whether it's a complete list of events in their lives, or a set of predispositions or potentials that may or may not be realised. A reason incidentally why two twins may lead quite different lives, even though their charts are almost identical.
One final point for the moment. Does the techniques an Astrologer uses determine the nature of the forecast in terms of Fate or Free Will? My answer would be no. One can use the techniques that Dave uses and put forward an extremely dogmatic and deterministic forecast, completely different from one that he himself would make. The reason would lie in the philosophical outlook of the Astrologer. In the same way, one could use the techniques of Vettius Valens, who was a stoic and a strong believer in Fate, and make a forecast that allowed for the subject influencing the outcome.