A fascinating article in Psychology Today ("Why Quitters Win") describes the results of a long-term (more than two decades) study of over 12,000 individuals that found that, aside from the expected contributors to success (family background and socio-economic circumstances, grades, SAT scores, etc.), one powerful indicator is an aptitude for decisiveness, "the ability to choose one course of action...while quitting others."
Here's the key paragraph: "At the heart of strategic thinking is the ability to focus on one strategy while consciously quitting the pursuit of others. Choosing what we want to do is easy. It's choosing what else we want to do that we are nonetheless going to quit doing that is the hard part—to build the school by stripping funding from the hospital; to develop this product while shutting down production of that one. As David Packard (of Hewlett-Packard fame) once said 'more companies die from overeating than starvation.' The same truth applies to our careers and personal lives."
It brings up a good point for managers, too: are you (and your operation) suffering from overeating (in Packard's term) or starvation? Are you focusing on too many things (and doing them badly) because you're unable to choose what to focus on?