What Stops Us From Playing Our Best Golf?

Why do we falter at golf? What stops us from playing our best golf? Why do we fail to execute shots we know we can hit? Now, I am not talking about those miracle shot attempts but the stock standard stuff like pitching, chipping, and straight forward short putts. Why do we fluctuate so much in our abilities to play steady golf? This unreliability is what makes the game of golf so infuriating and maddening to us amateurs and hackers. Is it too much to expect that we can strike a small, dimpled sphere reasonably straight toward a pretty generous target? The evidence, in my own experience of late, suggests it may well be.