Each year thousands participate in the U.S. medical school admissions cycle hoping to gain the privilege of training to become a physician. Every year admissions committees evaluate thousands of applications on the basis of their competence, personal characteristics, and motivations. Some applicants receive several interview invitations whereas others receive none. Contrary to the words of your consoling friend, this is not a numbers game any more than business sales is a numbers game. Being successful in the application cycle relies on understanding the nature of what both parties stand to gain from a successful transaction.
Admissions cycle as a sale
For some reason, very smart people hate selling. Sales is dirty. Sales is deception. Sales is uncomfortable. It's really not. Sales is about discovering whether or not two parties both have something of value to exchange. A sale happens if and only if both parties find the transaction beneficial. The most effective sales pitch will feel like education, allowing a client to figure out how to best meet their needs. An effective salesperson will deeply understand the client perspective and present appropriate information to drive the client toward a decision. Similarly the admissions cycle is a sale because the applicant is honestly selling themselves to the admissions committee as their client. The better the applicant understands the committee's interests and motivations, the easier it will be to help the committee understand how the student fits into their vision.
What do medical schools gain from accepting students?
Medical schools want to increase their ranking and prestige as an academic institution. They are incentivized to design a matriculating class to accomplish that aim. Several key performance indicators exist for medical schools including board exam scores and residency matching. Each student they admit is an investment; they are hoping the student will take advantage of the institutional resources over the course of four years, do notable things, and match into competitive residency programs. With more competitive match data, the school can recruit more competitive applicants in a virtuous cycle. With better statistics and an overall more impressive student body, the school has a better chance at securing private donations and increased state funding if they are a public school.
Two factors: competence and motivation
Medical schools evaluate a student's competence to ensure they can handle the academic rigor of medical education. They evaluate motivation to ensure the student will actively contribute to the scholarly community and continue to increase the notability of the institution. Competence is largely evaluated by metrics such as the MCAT and grades. Motivation is measured through essays, letters of recommendation, and interviews. Competence is not a rare. Motivation is. Plenty of smart students apply to medical school who actually have little genuine interest in medicine. I have multiple colleagues of mine who aren't enjoying medicine, have no interest in patient care, or have actually dropped out to pursue other fields. The admissions committee wants to avoid accidentally accepting these students because their productivity in medical school is unlikely to match that of the motivated student.
Proving motivation
Motivation is hard to prove. How do you know you want to go to medical school and be a physician if you've never done it before? Motivation comes from doing your homework and knowing what you're getting yourself into. Motivation comes from activities that suggest a stable interest in medicine for at least the past few years. Experiences such as shadowing and clinic volunteering are not intrinsically impressive, but if you've made critical observations about how medicine is practiced and can have intelligent conversations about medicine through your essays and interviews, now we're talking. Reading about the healthcare system and recognizing physicians don't operate in a vacuum can help you develop a meaningful interest in what you want to accomplish as a physician beyond "taking care of those in need" and "helping humanity". This sort of motivation is more convincing.
Answer the question Why Medicine?
Every year, there is one essay prompt that never changes. Why Medicine? Even if you are asked to submit a personal statement in lieu of answering an explicit prompt, your statement should answer this question. Yes, your essay should introduce who you are as a person, but your essay is really an argument for why you are choosing medicine. As opposed to nursing. As opposed to healthcare administration. As opposed to software, finance, or anything else more lucrative when accounting for the number of lifetime hours invested into your career. Choosing medicine for many is a deliberate choice, hopefully one you've thought about sufficiently. Some tell that story in one focal event, others take a life narrative approach. Others abstractly philosophize. The bottom line is you should actually discuss your interest in medicine, communicate your understanding of what it entails and present evidence that your decision is educated and deliberate. As you present yourself honestly as you are, it is my hope you are what someone else seeks.