Why is Google's CFO stepping down? To spend more time with his family, of course.

That's the excuse you always hear when execs leave, but the 52-year-old says he really means it.

"Yeah, I know you've heard that line before," said Patrick Pichette, in an unusually intimate blog post.

He said the decision was prompted by a question his wife Tamar asked him on a vacation to Mt. Kilimanjaro in Africa. She suggested they extend the vacation with a round-the-world trip. He responded it wasn't time yet.

"But then she asked the killer question: So when is it going to be time? Our time? My time? The questions just hung there in the cold morning African air," he wrote.

Pichette, who has been Google's CFO for 7 years, described himself as a member of FWIO, the noble Fraternity of Worldwide Insecure Over-achievers. He said he's been working a frenetic pace for nearly 30 years.

"The short answer is simply that I could not find a good argument to tell Tamar we should wait any longer for us to grab our backpacks and hit the road - celebrate our last 25 years together by turning the page and enjoy a perfectly fine midlife crisis full of bliss and beauty," he wrote.

Pichette likely has plenty of cash, though he is leaving money on the table.

He has more than 60,000 stock options that will not vest until next year, worth about $14 million if he could cash them today. He also may lose stock awards worth about $16.8 million at current prices. His base salary and cash bonus in 2013 and 2012 were about $3.5 million a year. His blog post does not discuss any of these financial considerations.

But his conclusion indicates he wasn't thinking about money.

"In the end, life is wonderful, but nonetheless a series of trade offs, especially between business/professional endeavours and family/community," he wrote. "And thankfully, I feel I'm at a point in my life where I no longer have to have to make such tough choices anymore. And for that I am truly grateful. Carpe Diem."

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