Core competence, as it is used by many managers, is a dangerously inward-looking notion. Competitiveness is far more about doing what customers value than doing what you think you’re good at. And staying competitive as the basis of competition shifts necessarily requires a willingness and ability to learn new things rather than clinging hopefully to the sources of past glory. The challenge for incumbent companies is to rebuild their ships while at sea, rather than dismantling themselves plank by plank while someone else builds a new, faster boat with what they cast overboard as detritus.
— The Innovator’s Solution: Creating and Sustaining Successful Growth by Clayton M. Christensen, et al.