"Was there a way of not going 100 miles an hour and maybe going 50 miles an hour? To be perfectly honest, I didn't explore that option. I never explored it," he said, describing his management style as trying to work as hard or harder than anyone else. A part-time position would have felt "inconsistent" with his style, he said.
El-Erian's departure rocked the investment world, where he was seen as the successor to "Bond King" Gross. Questions arose about the relationship between the two, and plans at Pimco, a unit of German financial services giant Allianz.
His reason for leaving is a cliche of departing executives: the wish to spend more time with family. El-Erian said that he decided it was more important to be a good dad than a good investor.
Read MoreBill Gross: Pimco is one big 'happy kingdom'
He realized he needed a change in May 2013, after his then-10-year-old daughter wrote him a list of 22 milestone events in her life he had missed.
In the wake of El-Erian's resignation, Pimco named six deputy chief investment officers, reporting to Gross, who is 70. Previously, there were no other CIOs but Gross and El-Erian.
Pimco investors, who this year have pulled $25 billion from Gross' Flagship Pimco Total Return Fund, the world's largest bond fund, have also been rattled by the shakeup.