The person I'd like to talk about is Mr Mendoza, the owner of a car repair garage in Monterrey, in Mexico, where I did an apprenticeship when I was eighteen.
The mistake I made was quite serious. About three months into the apprenticeship, I was asked to change the oil in a customer's car. I was in a hurry because I wanted to leave early for a football match, so I didn't tighten the drain plug properly. The customer drove off, and about twenty kilometres later the oil started leaking. Luckily she noticed the warning light and stopped, so the engine wasn't destroyed, but we had to tow the car back and repair it for free. I was sure I'd be fired; another apprentice had been sent home for less.
Instead, Mr Mendoza called me into his office the next morning. He made me phone the customer myself to apologise, which was horrible but fair. Then he told me I'd work for a month alongside his most experienced mechanic, checking every job twice and signing a checklist. He said, "Everybody makes one big mistake. What matters is whether you make the second one."
At the time, I felt ashamed and also hugely relieved. Looking back, I feel grateful. That month changed the way I work. I still use a checklist for every single job, even though I've been a qualified mechanic for six years now. I think if he'd fired me, I'd probably have given up on mechanics altogether. When I train apprentices now, I try to remember that a mistake is a chance to teach, as long as the person is willing to learn from it.