It’s hard selling your baby—and by that I mean a company you founded, not an actual baby.

Take Jeffrey Katzenberg, the former CEO of DreamWorks Animation dwa . He started the studio back in 1994 (it was originally part of DreamWorks SKG, which he founded with famed director Steven Spielberg and music mogul David Geffen). The animation studio went on to produce 32 films, including Shrek and How to Train Your Dragon. There were also some duds along the way, but the end result was a fruitful one: Last month, the company sold to Comcast for $3.8 billion. Katzenberg, meanwhile, walked away from the deal with an estimated $400 million. The only catch? He says it wasn’t his plan to leave—a condition of Comcast’s cmcsa .

I profiled the longtime studio exec in the most recent issue of Fortune. “Of course,” he told me when I asked if selling his company was hard. “It’s my baby, and I’ve spent 22 years here. My work is my happiness and my happiness is being here at DreamWorks.”

The $400 million or so that he received should help soften the blow. But for many CEOs—especially those who start and stick with their offspring well past infancy—walking away can still be tough. Katzenberg’s recipe for reinventing himself now that the longest-running chapter of his career is over? Speed. He has already thrown himself into the next venture: running his own investment firm, which he says will focus on the convergence of media and technology. And while the transition isn’t pain-free, he doesn’t look back, and wastes no time being nostalgic or remorseful.

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Letting go and moving on is an important lesson for all CEOs. Of course it’s easier if you’re driving away in a white Tesla Model S, like Katzenberg. Or leaving with a massive golden parachute. But even some of those privileged execs take way too long to exit. Silicon Valley is no different. Yes, founder CEOs who are still running the show are revered for a reason. But sometimes, the best thing you can do—for yourself as well—is to walk away. Go start another baby.