You don’t need a single epiphany. In fact, this is likely to do the opposite of conveying your motivating for medicine because it’s actually only conveying your initial impulse for studying medicine.
I’ve read so many unconvincing opening paragraphs on the examples on TSR that centre around being suddenly inspired to study medicine by a freak accident they witnessed or by watching their grandparent being wheeled off by paramedics. You can practically bear people rubbing their hands at the prospect of such trauma and it’s a bit twisted really.
Most people’s motives for medicine are around wanting to help people and having a meaningful career. And for a large majority money will factor in there somewhere. The obvious riposte to this is, well why not nursing, or teaching, or physiotherapy, or occupational therapy, or an accountant? You’ve basically got to try and convey your understanding of what makes medicine unique among these and why you are particularly motivated by this. Then there’s the obvious riposte to this which is, well how do you know medicine will meet your expectations? And how do the admissions team know that you’re suited for this kind of work? This is where your work experience and volunteering commitments/positions of responsibility come into it. Your personal statement basically makes the case that your decision to apply to medicine is an informed one.
Your opening paragraph of your PS should try and summarise your reasons (plural), and should just be sensible. There are only so many ways for a person to say they want to study medicine. They’re not expecting a unique and individual reason from every single person applying. They’re just wanting to see that you’ve developed your motives beyond that initial impulse, which is not always the most mature or the most informed reason. If I were focusing on that initial impulse, I was inspired by a rather petty moment where I got annoyed with a doctor in the unit where I work and thought, “I could do that better than you” and then part of my brain went, “go on then, prove it” (and another part of my brain went, “oh god not again”). Needless to say that didn’t make it into my personal statement and nor should it. It has very little to do with the reflective process I undertook to get me to the point where I decided to overrule the “oh no not again” part of my brain and listen to the part of my brain that was able to engage in that honest simple reflection. One person’s amazing story about witnessing a heart attack on a mountainside and being awestruck by a randomly passing GP’s actions in saving the person and being forever inspired to study medicine from that moment onwards (actual PS example on TSR) is not something you need to compete with. That’s not what they’re selecting for.