A quote from Colin Wilson

“The human mind tricks itself into underperformance. Humans too easily fall prey to unnecessary defeatism. Certain kinds of experience trigger our full capabilities, e.g., on receiving surprise good news we get a sudden surge of enthusiasm, optimism and meaning. When we are threatened, we suddenly spark into action.”

From your own life, you know this is true. But does that mean that we are controlled by the chemistry in our brains, which are trigged by positive or negative news?

Among that and many other things, I would say yes. But I find myself decidedly in the behaviouralist camp with Skinner and such. I think the notion of “free will” as something sourced from the conciousness is very much an illusion. Sure it exists, but before we are aware of it, decisions are made.

The funny thing is that we can trick the chemistry by our own thoughts. Yesterday I heard bad news and started to feel sad. But I was also aware of doing so. This awareness made it possible for me to argue with myself and I was able to escape the sadness.

Yes, the process you are describing does indeed exist, but you noted yourself that it took awareness, concentration, and mental energy to do so. It isn’t something you could keep doing all of the time without getting very tired—and you wouldn’t have much attention and energy left for other tasks. I like to compare consciousness to the rudder on a sail-boat. You can make course adjustments and manipulate the attitude of the boat to the wind, but the wind (autonomic factors and so forth) will always be the dominating factor.

The neat thing is that continual pressure against impulse can, over time, cause us to change. But again, we are just influencing our defaults. Those defaults are still going to be the driving force, and in most situations in life, that is what we are driven by.