Years ago, while consulting with an oil and gas company of globally recognized name, I asked about a process that did not seem to work well. The response I received from a successful middle manager was, essentially, this: "Yes, it is flawed and we know it doesn't work well. But we're comfortable with it and have no plans to change it, because we can implement this process quickly."
Using a flawed, but speedy process makes absolutely no sense. And yet, it's what many of us do multiple times each day. We keep doing something the way we know, rather than the best or better way, because we have so much invested; the sunk costs (whether financial or emotional) keep us from thinking clearly and charting a course to what would work far better.
This is one of many places in life and in work where the risk of failure is high--not because we've already failed, but because we refuse to ignore the siren song that lures us to stay where we are and feed the sunk costs. If failure is inevitable in a life of exploration and learning, perhaps we need traveling companions who do not allow us to succumb to the sirens.