Salesforce CEO Marc Benioff is now one of the most powerful leaders in Silicon Valley, but 30 years ago, he was a young, aspiring entrepreneur just starting off his career.

It was Oracle CEO Larry Ellison, now the world’s fifth-richest man, who took Benioff under his wing and turned him into a star executive.

Although their relationship had its ups and downs through the years, Benioff wrote in his 2009 book, “Behind the Cloud,” that Ellison is his “mentor” and “close friend.”

He even dedicated a small section, called “The Larry Ellison Playbook,” where he lists the seven lessons he's learned from Ellison.

“Many of the lessons I learned from Larry still guide me today,” he wrote.

Benioff was only 23 years old when he won the Rookie of the Year award at Oracle. By 26, Benioff was a star executive at Oracle, making over $300,000 a year.

Benioff became close friends with Ellison during his 13 years at Oracle. So close that some people even wondered if Benioff was Ellison’s nephew.

Ellison was a strong supporter of Benioff when Salesforce first launched in 1999. He was one of the first seed investors and even let Benioff work at Oracle until Salesforce really started to take off.

But the two had a falling out when Benioff discovered Ellison had secretly started his own CRM product that directly competed against Salesforce. Benioff eventually made Ellison resign from Salesforce’s board.

For years, the two formed a fierce rivalry, often trash-talking each other publicly. But they largely remained mutually respectful to each other, with Benioff calling Ellison his mentor. Here are the seven most important lessons Benioff says he’s learned from Ellison:

1. “Always have a vision”

Ellison and Benioff are each credited for transforming the database and software industry, respectively. Ellison, in fact, shared the vision for cloud software early on and provided seed money for Salesforce and NetSuite.

2. “Be passionate”

Ellison and Benioff are probably two of the most competitive and hardest-working CEOs we’ve seen in a long time. Ellison once said, “I’m addicted to winning. The more you win — the more you want to win.” It also says a lot that he refuses to retire even at the age 71.

3. “Act confident, even when you’re not”

Ellison’s self-confidence is almost legendary. Benioff is equally confident all the time, and they’re both not afraid to trash-talk their competitors in public. “[Ellison] taught me that accomplishments are fueled by faith,” Benioff writes.

4. “Think of it as you want it, not as it is”

Benioff famously moved his 10-person team to a new 8,000-square-foot office in 1999. One of his cofounders, Parker Harris, was upset that Benioff got such a big place, but Benioff simply told him, “We’ll be out of here before you know it.” One year later, they ran out of space and moved to a bigger place.

5. “Don’t let others sway you from your point of view”

When Benioff first shared his idea for Salesforce with cofounder Dave Moellenhoff, he was told it was a “crackpot idea.” That didn’t stop him from pursuing his vision for a cloud software, and now Salesforce is a $50 billion software empire.

6. “See things in the present, even if they are in the future”

Benioff says people used to joke that Ellison got his tenses confused because he was always thinking about the future. “A successful leader is one who is always thinking about the future, not just the present,” Benioff writes.

7. “Don’t give others your power. Ever”

This partly explains why both Ellison and Benioff continue to keep a tight grip on each of their companies, even after all these years. Also, it's one reason why it’s unlikely Benioff will sell Salesforce anytime soon.

This story first appeared on Business Insider