Never say anything's 100 percent sure. Lucky people know that some of their decisions will be wrong, so even though they take risks they don't set themselves up to fail by expecting success to hit every time.
Don't push it. People who are lucky always assume that their luck will run out. They sell short and don't ride the peak, because they know not to push their luck. It's not about being a pessimist but a realist, with a rational approach to a world that is uncontrollable and unpredictable.