You probably failed the first time you tried to sit up as a baby, but no one gasped in horror and whispered about a wasted life. At least, I hope not. And then you tried again...and...again, until one day you made it. For about five seconds and then you toppled over.
You probably fell over a lot those first few months trying to master the fine art of sitting up and staying up. Heck, I've fallen over once or twice since then myself. But you never gave up and no one ever, ever thought to tell you it was time to give up. Again, at least I hope not.
So failure, once upon a time, was expected and accepted. We were encouraged to keep trying because it was the only way to strengthen our muscles so we could eventually sit up...and crawl...and walk. You get the idea.
So what happened? When did we became afraid to fail? When did it become shameful to try and not succeed? We probably shame ourselves more than any one person, but I know people who like to point out others failings as if it proves something is wrong with them.
But failure is actually a symptom of effort. Failures are the people who don't give up after just one failed attempt...or 100. Failures keep trying new things until they succeed. And I for one am proud to count myself as one. I'm in good company, too. Some famous failures are Albert Einstein, Stephen Hawking, Oprah Winfrey, Steve Jobs, Micheal Jordan, the Beattles, and Eminem.
So ultimately we fail because we take a chance on new ideas, we step outside our comfort zone, and in general, because we try.
If you've never failed, you've never tried anything new.