Belinda Carlisle passed on her morning workout, a 6 a.m. ritual in her Los Angeles home. She was out real late with friends the night before, she explained.

Of course, "real late" for Carlisle these days is 1 a.m., positively puritanical by pop star standards.It wasn't like that four or five years ago, when the singer was a member of the Go-Go's, the most successful all-female pop band of all time. Back then she was into all-night binges, drinking and drugging her way through the fast lane. "We Got the Beat" indeed.

So the group's rancorous 1985 breakup proved to be one of the best things that has happened for the 29-year-old singer, who's now a successful solo star. She went into treatment to kick the drugs and booze, shedding 25 pounds in the process. She also fell in love with and married film producer Morgan Mason, son of the late actor James Mason.

"I basically started over," she said.

Second chances should always be so good. Carlisle's 1986 solo debut, "Belinda," sold a million copies and launched the hit single "Mad About You." But that pales before this year's "Heaven on Earth," another million seller with three big hits - the title track, "Circle in the Sand" and "I Get Weak" - and a just-released fourth single, "I Feel Free," that is expected to do just as well.

"I do think of my albums as more polished than the Go-Go's," Carlisle said, adding that she considers that a favorable difference. "With this album, I had the production I always wanted in the Go-Go's. . . . The Go-Go's were great for me, but I wanted to go beyond that."

When the end came, Carlisle wasn't so sure she'd equal the group's success. The Go-Go's sold more than 7 million records between 1981 and 1985 and, thanks to lots of smiles and bubbly personalities, were the darlings of the American pop audience.

In some ways, though, it seemed almost too easy. "We were accepted from the beginning and really loved by our fans," Carlisle said. "We forgot that things usually don't come that easily."

And that, of course, made for a scary sojourn into the solo world. "There were a lot of people who wanted not to like me," she said. "I felt that I really had to prove myself."

With that accomplished, however, don't expect to see Carlisle take the next step favored by many pop stars - into films. She's taken acting classes as part of a development deal with Walt Disney's Touchstone Films, but "after three months, I lost interest. To be a good actress, you can't be inhibited, and I think I'm still a little too self-conscious right now.

"And really," she added, "I'm happy enough being onstage and making music. I feel really lucky that I was able to live through the Go-Go's experience and survive. I'm happy and I'm doing well and I know I'll never get to that point again. I've learned too much to let that happen."