Happiness is very different from survival. The human machine - our bodies and minds - evolved to increase the chances of our survival and the continuation of our genes and our species.

The mechanisms that helped us to survive don't promote happiness. In fact many mechanisms that helped us survive do just the opposite - they make us unhappy. They also promote illness and a loop of perpetual stress. Here are some examples:

1. Negativity Bias - this is the tendency to see or seek out possible dangers in any given situation. The mind evolved this capability in order to protect us from danger - real or imagined. Better to imagine a danger that isn't there than to miss a danger that is. By being ever vigilant to danger, we prevent ourselves from being eaten by bears. We also increase our own tendency to see the negative side of our client's request for changes and that new corporate policy.
2. Fight or Flight Hormones - These are hormones that are put into the body when you are under stress. They help you handle short term bursts of danger, but they cause long term break down of the body's systems. They were designed to be introduced when very significant immediate stressors were placed on an individual to power survival, they did not evolve to meet the demands of day-to-day stress of the modern work place where fighting or fleeing is not terribly useful.
3. Chaotic Heart and Breathing Rhythms - this was also part of the fight or flight response and it evolved to AVOID the use of higher brain functions in times of immediate physical danger. When heart and breathing become chaotic they suppress higher brain function, this is why we may feel like our brain is not helping us out when we are 'on the spot' or 'on stage'. This is because the stress is causing erratic heart and breathing rhythms which impair our higher brain function.

The good news is that we understand all of these things now. We know that it is happening and we can do something about it.

The trouble is there isn't a traditional class you can take or procedure to address these things. They're emotional and physical and you must practice self-awareness in order to be aware that they are happening to you and do something about it.

The last two points come from Coherence by Dr. Alan Watkins, which I am currently reading. It is an excellent book and I recommend picking up a copy if you are interested in the human condition, physiology, business leadership, and the overlap of all those things.