Before he became the most powerful banking chief in America, JPMorgan Chase CEO Jamie Dimon set himself a simple career rule that sounds almost radical in the age of personal branding: Keep your mouth shut. As a 28‑year‑old Harvard MBA working as an assistant to American Express president Sanford “Sandy” Weill, Dimon wasn’t focused on “being visible” or chiming in at every meeting, but rather soaking everything in.“My first goal was to learn something and not say anything until I could add some value,” he told Fortune in an early-career profile which has resurfaced on social media.

At the time of publication, the fresh-faced Harvard MBA had just been promoted to vice president—climbing the ranks from his position as Weill’s assistant in as little as two years—when he shared the career tip.

Before then, he’d already helped analyze multimillion-dollar deals and negotiated major acquisitions. Yet his instinct was still to earn the right to speak.

And it paid off: One year later, he went on to follow his former boss Weill to Commercial Credit, where he became its CFO at just 30 years old.

Jamie Dimon’s mantra for Gen Z: ‘Learn, learn, learn, learn, learn, learn, learn’