First let's consider the essence of God's plan. Since God is perfect and holy, He could not have needed us. I believe God wanted us. He wanted us to love Him without making us mindless robots. Because He Is all knowing, He knew allowing us to make choices would result in our becoming unholy and separate us from Himself. He provided, in His plan, a way back to Him through the sacrifice of His son. Beyond this, much of God's plan remains as mysterious as He is. That doesn't mean He doesn't have the details worked out. It simply means we don't know the details. Part of that mystery is what role we play in it.
Now let's think deeply about God and time. Ravi Zacharias says that " God is the only enity in existence, the reason for whose existence is in Himself; all other entities or quanities exist by virtue of something else and in that sense He alone is perfect, uncaused, infinite and independent being in essence." It's more scientific than you might think. New experiments in quantum mechanics have shown effects can happen before the cause. The bible teaches in Revelation God is "the Beginning and the End." God can operate outside of time and space or from whatever, whenever, or wherever He chooses. He can operate simultaneously from any point of time because He is eternal. This means it's possible for God to interact with you in real time, without reacting to you, though He included your actions (or lack of) in His plan. So pray, it means you can't rule out that your prayers might be a part of the details of God's plan. Think of it this way. Suppose you were planning to put together a bike for your child. If you decided to let your young child help, would you still be in control regardless of the mistakes you know your child is going to make? Would it make him love you if you forced him to help? Would still want your child to talk to you during the process? At the end of the day, wouldn't you still have a bike?