We really can't handle the truth: Hollywood legend Jack Nicholson is retiring from acting.

Nicholson, 76, quietly stepped down from a 50-year career. "Jack has -- without fanfare -- retired," an insider told Radar Online.

The rationale behind his decision has to do with his aging.

"There is a simple reason behind his decision -- it's memory loss. Quite frankly, at 76, Jack has memory issues and can no longer remember the lines being asked of him," the source revealed. "His memory isn't what it used to be."

Nicholson, who was nominated for a record 12 Academy Awards for acting (winning three), will continue enjoying the spotlight -- just not starring in it.

"Jack has no intention of retiring from the limelight," the source said, noting the Oscar winner's regular courtside Lakers games and Academy Award presentation with First Lady Michelle Obama in February.

"He's not retiring from public life, at all. He just doesn't want a tribute," the source said. "He's happy to tacitly join the retirees club like Sean Connery."

We'll miss you, Jack!

More From Power 95.9