Are you free to decide your own fate or are you predetermined by outside forces?

This is only an opinion, just as everyone else has. I will state it in a factual manner, but only because it makes the typing more simple. I believe that your actions, as well as the positioning of the celestials, determines the outcome of your next "reaction" or "move", if you will. The human mind is a powerful tool that even Nanotechnology doesn't understand. There are many things that can be done with the human brain that has yet to be explained. Let's just say that life is what you will "make of it". Those outside forces that you speak of, are connected to the inside forces in your own body. It is the energy that flows through you that gives you the mobility to make the choices that you do, be it Plan A, or Plan B. The forces (we will just call it energy) will be influenced by the positions in the heavens, as I have stated before. This does not leave room for a definite. There are too many choices pulling each other one way to the next. Your brain will make it's choice according to which of these different energy fields may either be strongest, or that it has decided upon from willpower over others. In my conclusion, I will lean more toward the idea that you would be more likely to make the decisions that will draw your own blueprints for this life filled with countless amounts of energy on your own.