Starseed hit it perfect.
It's the Ego's attachment to outcomes that leave you feeling unfulfilled. A goal is just an idea of something that could be possible. It becomes empowering when you imagine it as somewhere you would like to get to and work towards getting there, it guides your thoughts and actions in making it happen.
As soon as you get attached to outcomes of goals however you feel empty, it's because you "aren't there yet", and sometimes it feels like you will never get there. You create a goal as somewhere that has to be reached and that something is lacking if you don't reach it or worse, something is lacking until you DO reach it. This is what it is to chase goals, to go after them trying to have that right goal fill that emptiness that comes from thinking you are lacking and that's where the experience of disatisfaction comes from.
Raising your awareness allows you to see the connection between outcomes, and goals, and the attachment, separating one from the other. You start to live in the now again, and become connected to what is real and happening in the present. Everything just as it is right now is perfect with nothing lacking, then goals become ideas of something possible again, not something to hang onto.
That sense of lacking is actually not a function of the brain, it is a learned concept that is common in almost all people. Psychology, not physiology. The fact that many people have unlearned it to go on to experience fulfillment in their lives and still have goals they want to achieve, shows that the two can exist at the same time.
Lastly, Radical: RT Wolf said something that rang with me, your posts do have a generally nihilistic tone. Is there a reason for such posts? Because living in a world like that would be hell.