It's more like a tool to glean insight on the root of your challenges, shed light on gifts/talents, and overall increasing awareness of self. You can use it to get a feel of challenges and narrow that down to a specific theme or area in your life, while also discovering how to make the best choice in order to experience the best outcome.
So in a sense it can be seen as a blueprint but ultimately you have free well. That does not negate the fact that you are here for a purpose and life experiences will shape itself to fit the theme of that purpose.
You can discover the best way to respond to these experiences using Astrology to gain a deeper understanding of self, mentally, emotionally, and spiritually.