Sir Jackie, 70, who won three Formula One World Championships in the late 1960s and early 1970s, said the deaths of 57 drivers in an 11-year period during his career had a traumatic effect on him. At the time he was able to suppress his emotions so as to continue in competitive racing but now, in retirement, he grieves for their loss.
They include seven of his closest friends, including two-times Formula One world champion Jim Clark, whose Lotus-Cosworth somersaulted through the air and smashed into a tree during a Formula Two race at the Nürburgring, Germany, in April 1968.
Sir Jackie, speaking on BBC Radio Scotland's Stuff of Legends, to be broadcast tomorrow, said he was able to "block out" his grief at the time in order to perform. But he said the mental and emotional "scars" had emerged in later life.
He told interviewer Bryan Cooney: "When I was racing I could block it off very successfully – because it was sadly an occasion that was too often happening, with such regularity in some cases that it was absolutely shocking. When I look back in my life at those moments, for whatever reason, I was able to almost remove emotion and grief. I can't do that now.
"I have a belief that there was a wee sack of something round my heart, a fluid that somehow was able to dilute my grief as it was happening. That saved my life and allowed me to continue and do the things that might otherwise have been difficult to do. I think it happened so often however that the reservoir went dry. So today I quite often find myself more emotional than most people would ever think Jackie Stewart would have within him in the way of sorrow.
"Because, when I think back, I saw things that a man or woman should never see. They were real scars into my mind and emotional balance. At the time I was able to block them off, but every now and again they return and they will never be forgotten."