One very important part of building self-confidence comes from the people you have around you on a regular basis. Having someone unstintingly supportive in your life can have an amazing effect on your view of yourself. I know how incredibly lucky I am that my father was such a positive person. Without his unwavering support, I would never have gotten through college and medical school, where some of my teachers told me I was useless and stupid. During my freshman year at college, one chemistry professor actually told me that I “would never be any good, never graduate, and never, ever get into medical school.”

My father’s response was, “Wait a minute. You just started college—what does he know? I’ve known you a lot longer and I know you can do it.”

Thank goodness I had such a loving and wonderful father. He made me realize that we all need to have somebody—a child, a partner, a friend, a colleague—who believes in us and who will always stick up for us . . . even when we might make stupid or thoughtless mistakes. We need to be reminded of our positive attributes during times of crisis. We need someone to call without the fear of judgment.

My father was this essential friend to me. I knew I could call him when I failed a test or messed up something else, and no reproach would come. Instead, he always made me feel better. More important, he would randomly note something I’d done well during the course of the day. That type of positive reinforcement was so effective when I was a vulnerable young man. He helped me believe in myself, which, in turn, made it possible for me to ignore hurtful criticism and take constructive criticism for what it was. To this day, when times get tough for me, I simply close my eyes and remember my father’s kind and reassuring words, and this allows me to move on, endure, and succeed.

You too can feel the comfort of encouragement you received in the past. Whenever you need to, simply stop and take a minute to remember a time when you felt empowered or appreciated. If it’s a particular memory, visualize yourself in that moment. Remember the scene, the smells, the feelings. If it’s a general memory of someone who was always there for you, visualize that person—his appearance, the tone of her voice. Bring these comforting memories fully into your mind, and you’ll be amazed at the power they have. And if ever you need more encouragement than can be provided by a memory, don’t be afraid to reach out to the people in your life. There’s no harm in asking for support, and the love you receive could change your life.

One of the best things that happened to me to boost my self-confidence took place during my rotation at New York Hospital, 25 years ago, when I was a lowly medical student with a chip on my shoulder and an inferiority complex larger than the Brooklyn Bridge.

Because I was being snubbed by the other medical students who’d gone to more prestigious schools than I had, I hung out with the nurses, who were much more tolerant of my humble credentials. Plus they knew a hell of a lot more than my fellow students gave them credit for. Actually, I already knew that, as my father always advised me to listen to nurses carefully—their clinical experience can be vast since they are the medical professionals spending the most time with hospitalized patients!

Those nurses were really wonderful to me. One day, I watched as they treated someone with a bad electrical burn. The head nurse explained that if you grab an outdoor power line, the high voltage instantly travels through your body, and causes an average limb loss of 2.2 (as in two limbs that are so damaged that they’d have to be amputated).

Soon after this, the chief surgeon in the burn unit, who was a brilliant burn expert who’d written many textbooks and was viewed with awe, even by the most arrogant medical students, was leading a treatment team meeting. Unfortunately for us, the surgeon’s second-in-command loved torturing the residents, asking them really difficult questions to make them look stupid—just because he could.

On this infamous day, the second-in-command said, “Let’s talk about the patient with the electrical burn. Here’s an easy question. What’s the average loss of limb for this kind of injury?”

The residents didn’t know. The Cornell medical students had no clue.

“Are you telling me that nobody in this room knows the answer to this?” he went on.

By now, my friend who was the chief nurse was looking at me with her eyes on fire, so I raised my hand and quietly said, “I think it’s 2.2.”

The chief surgeon was so impressed that he started engaging me in more things and ended up giving me a phenomenal letter of recommendation. I had found someone who believed in me, and it completely changed my life. He, and that wonderful head nurse, gave me the self-confidence to speak up, whether I was sure of the answer or not. Having people like that on my side helped me achieve my goal of becoming the best possible surgeon I could be. I didn’t want to let them down, and I didn’t want to let myself down, either.