One of Scotland's greatest painters, John Bellany, has spoken of the daunting task of facing mortality, his forthcoming landmark exhibition – and a new self-portrait which defines him at the age of 70.

In a revealing interview in today's Herald Magazine, Bellany – known for his powerful depictions of the sea – says he feels that he is currently in a "netherworld between life and death."

More than 20 years on from a liver transplant, the painter, whose retrospective exhibition John Bellany: A Passion for Life, opens at the National Galleries of Scotland on November 17, is still painting in earnest every day even though he is suffering from a variety of ailments and is currently recovering from what he calls a six-year depression.

A new self portrait in the exhibition, he says, sums up his thoughts about turning 70 and still existing as a working artist.

"It's like one of Rembrandt's last paintings," he says, "It's about approaching the Almighty – really you are in that netherworld between life and death when you are 70."

Last night, John Leighton, director-general of the National Galleries of Scotland, said: "John Bellany is a key figure in the history of modern art in this country and we are very proud to pay homage to his outstanding achievement with a major show at the National Galleries of Scotland."