'Batman' actor Michael Keaton reveals what co-star Jack Nicholson told him decades ago as he prepares to reprise his role as the Caped Crusader in the upcoming DC installment 'The Flash.'

Nicholson told the cast and crew he took every success as a green light for a little wiggle room while on set for the 1989 Tim Burton comic book film.

'When I was working with Jack Nicholson on 'Batman,' we were going somewhere, and he said, 'Come along with me,' and it was a whole new experience,' Keaton said during a Hollywood Reporter Drama Actor Emmy Roundtable with Oscar Isaac, Tom Hiddleston, Samuel L. Jackson, Brian Cox, and Quincy Isaiah.

In the car, he was talking about the movie. We all knew it would be a big risk, and if it failed, [I] would be going down in flames and that would be a long, difficult recovery. It also changed my landscape if it worked,' Keaton explained.

Keaton, however, said that such advice will no longer work today: 'Not now, man,' he said. 'You've missed one, and that's messed up.'

In a discussion with fellow actors, Keaton said it is 'impossible' today to say 'I'm going to cruise on this one' when it comes to even the smallest of projects and to deny your instinct as an actor to perform at your best.

'You get there and the work's the same, man,' Keaton said. 'Even if you're doing a 15-second Vaseline ad, you'll say, 'OK, man, I'm all in,'' he said. As a matter of fact, for that minute I don't know how to not be all in, not because I'm so fucking groovy, but because I'm afraid to lie down, of saying, 'Well, don't be a dick.

The advice Nicholson gave to the next generation of actors was also passed on to Bill Hader, creator, and alumnus of 'Saturday Night Live'. Keaton said he took a career break and 'laid low' after becoming a father, and he told Hader to do the same.

Keaton said of turning down projects, 'I thought, 'Man if I lose money, I'm good with it. He was going through something the other day, and I told him, 'Dude, trust me. Spend as much time as you can with your kids you can for as long as you can. In the long run, you will never regret it. You may lose some jobs, but it's okay.'