Being about to anticipate danger or react the fastest is likely a contributing factor to how we all got here. If you could outrun the saber tooth tiger, you got to pass on your genes. Those that weren't fast enough did not.
The pre-historic, primal part of our brain still exists. What gave us an edge millions of years ago cuts our legs out from under us now. Seth Godin calls it the "lizard brain." The lizard brain wants you to stay quiet, safe. Hidden. Unseen. Out of danger so that you can avoid becoming a tiger snack and survive. The lizard brain speaks orders of magnitude louder than our modern brain ever could. It doesn't respond to logic or reason (would you try to reason with an alligator?) and it will never be satiated by any amount of reassurance.
It's the voice that tells you that no one cares what you have to say, that you have nothing new to contribute to the world, nothing to offer. Or the voice that says, "See? No one is listening. Just stop while you're ahead." so instead of pushing through the dip on your way to becoming great, you become stuck in mediocrity. The lizard brain traps us into logic that ultimately creates self-fulfilling prophesies over and over again. Yes, if you give up, you'll always be mediocre.
The lizard brain helped us survive. It is what contributed to our evolutionary success. But in the post-industrial economy which will reward those of us who are the bravest, the most generous, the linchpins that dive head first into the emotional labor which is what the connection economy will require, the lizard brain is a well-versed saboteur. It's had millennia to come up with reasons to hide, excuses to stall, never-ending quests for reassurance. In a certain sense, what at one point gave us life threatens to snuff out our light hundreds of thousands of years later.