Sylvester Stallone is opening up about how he’s quietly suffered anxiety-induced attacks for decades … and how his diagnosis still plays a part in his life.

In a wide-ranging, candid interview with The New York Times, Sylvester said the first time he suffered from an anxiety-induced attack was when he was watching daily footage from a film project in his mid-30s.

He said … “The first timewas when I was 36 and I was watching dailies, and then all of a sudden I stood up and the hair on my neck went up and I started getting hot and I go, I’m dying, this is it, I’m on my way out. And bang, down I went. Took a knee, crawled, rolled over, and now I’m in this dark movie theater.”

While Sylvester didn’t label the episodes as panic attacks … he did say he suffered similar moments of crippling anxiety “again and again and again.”

The “Rocky” star said that the attacks come out of nowhere … and are something he still deals with as he gets older.