The great American humorist Mark Twain certainly spoke for me when he said, "The human race is a race of cowards; and I am not only marching in that procession, but carrying a banner." He certainly spoke for me - and for billions of others. However, it's important to distinguish between caution and cowardice, and I suspect that while Twain may have had the word "caution" in mind when he uttered that remark, he knew it wasn't a quotable moment if he started the quote by saying "The human race is a race of cautious individuals."
Natural selection rewards the cautious. At the slightest hint of danger, animals scurry for safety - only in human beings (and possibly the higher primates, I don't know) does curiosity overcome caution to any great extent. Another aspect of the animal kingdom with which I am unfamiliar is the extent to which rational decision-making plays a part. However, human beings have the ability to make rational decisions, and these decision often involve alternatives in which there are different degrees of risk involved. These decisions occur in all areas of human endeavor - personal relationships, business, and the quest for self-fulfillment.
So when does it pay to be cautious, and when should you take a risk? The general rule of thumb is that you should be cautious when you have a lot to lose, and you should take a risk when you have a lot to gain.