Timing is represented very peculiarly in the brain.
Your brain perceives sensory information
before it's actually created and contrastingly perceives your intentions and actions as coming
after they have already occurred.
When you move your eyes, for example, you do not see a blur of images. Your brain fills in the time that you took to move your eyes with what you next look at. You are tricked into thinking you've been looking at something slightly longer than you have. Sometimes you can notice this when you move your eyes to a clock or microwave timer. It can seem like the current second freezes for a slight instant longer than the others. This phenomenon has been described more concretely in several studies, but this is an easier way to describe it intuitively...
As for the timing of your intentions, EEG studies consistently show that the time you think you've decided to move or respond to something is well after spikes of activity that can predict your intention before you're even aware of it.
It's interesting that the brain goes to such an extent, fooling you by changing its clock in both directions, to give us the illusion of control. It makes me wonder, why bother? What benefit is there of this type of deception?
(Edited 4 minutes later.)
Also, OP, I don't agree that our "whole life" is planned in our brain. Is the whole life of a worm planned in its several hundred neurons? Although maybe you're just being rhetorical...
(Edited 25 seconds later.)
Predestination will set you free, OP.