There is nothing more dangerous believing you are successful, nothing in the past success guarantees any future success. It is your perception and capability that impact future success. Even things happening that are feelt to be out of you control you can still adopt to it, overcome it and finally learn how to live under uncertainty.
In Jim Collins new book, How The Mighty Fall: And Why Some Companies Never Give, you can read more about the five steps to check mate:
Stage 1: Hubris Born of Success
Stage 2: Undisciplined Pursuit of More
Stage 3: Denial of Risk and Peril
Stage 4: Grasping for Salvation
Stage 5: Capitulation to Irrelevance or Death
By applying scenario planning and risk management, defining and adopting your core capability to match a core need on the market within a unique competing space, driving for innovation, never giving up, always challenge yourself and never get fat and happy you have a rather good chance of getting a long successful track record.