Programmed?

As people are we programmed to fear confrontation? Do we resist the urge to spill our guts because there is a chance that we might say the wrong thing? Why do so many people sacrifice their voice in order to satisfy a doubt? To me, saying anything, right or wrong, is better than remaining silent. Its beyond crucial in some situations to speak your mind however very few actually take the risk. I've tried a million times to get out the words but my brain shuts down, my mouth begins to close and I change the subject. I've lost so many opportunities to turn my life around and to turn someone around with my words. To make them walk towards me instead of away. To put things in place instead of flying through tense air. So are humans just programmed to fear the unknown or have we grown into a bunch of nervous freaks too afraid to wonder out? Have we become paralysed before the accident even occurs?