Confidence shows

"Iraq’s expelling Khomeini in 1978, at the Shah’s insistence, gave him an even more effective pulpit in France where he remained until 1979, returning to Iran only after the Shah had fled, " Rodney explained the history of the Iran revolution to me over a kebab dinner. "The Shah’s crumbling self-confidence, the Carter administration’s refusal to provide him with non-lethal military aid and Khomeini’s resolve led to collapse of the care-taker Bakhtiyar government in 1980."

Confidence is contagious and so is the lack of confidence and a customer will recognise both.
Confidence means trusting in someone and relying upon them. Interestingly enough, it also means relying on oneself - self-reliance.
There's a saying: "A team that thinks it's going to lose is going to lose."