John Mayer encouraged aspiring songwriters to trust their survival instincts when it comes to developing their careers and go it alone if they can't surround themselves with trusted advisers.

"I don't want to teach people how to give a shit," he said. "I wanted to do it, I did it, it's done."

Erik Philbrook, editor of ASCAP's Playback magazine, interviewed Mayer on Thursday at the performing rights organization's 5th annual I Create Music Expo at the Hollywood and Highland complex in Los Angeles.

Mayer reflected on his 20-year career, noting that it was two decades ago when he was learning to play guitar and one decade ago when he got a record deal.

"Brutal truth number one is that the record deal is not the finish line -- it's the starting gate," he said. "And that contract says 'in perpetuity throughout the universe.' I can't cut a track with Kanye on Mars."

Mayer also took on his reputation for unfiltered speaking. "I love getting into trouble when I say stuff," he said. But Mayer says his much-vaunted use of Twitter really has two decent uses: thanking fans and cool links. "The last couple weeks, every night I think about deleting my Twitter account ... I think it's over," he said. "I think when I signed up someone should have said, 'Oh, do this, you can get half a million haters.' ... I think I should spend my time making a sandwich or building a model ship."

Mayer said he writes his music first, and then his lyrics, and a lot of tinkering is involved. "You sort of get this feeling that the Astrodome is opening up," he said. "It's always like when you're toiling on this thing for months and months and then this other thing was written in two days. Maybe you were working on this when you were actually working on that."

And Mayer expressed some sadness at the changing of the industry, remembering a time when he could hear the same song at home, in the car and then in a restaurant.

"There isn't one mainstream any more, there's a hundred tinier streams," Mayer said. In some ways, he said, it's great because everyone can "navigate their own stream," but "I miss the days of owning the world with a song."

The ASCAP Expo continues through Saturday.