The Australian singer, who is married to John Easterling, said that she is very "grateful" for the life she has now, because she has experienced painful moments in the past.
Newton-John told the Herald Sun: "I'm probably the happiest I've ever been in my life now. I'm in love with my husband, we have a really interesting life, and I feel like I'm doing things I want to do and helping people.
"Life is full of valleys and peaks and everybody has them. Everyone goes through loss and pain and it's all part of life. For me, I just became more grateful for every day. It's all icing on the cake now."
Newton-John is currently in Melbourne performing her A Summer Night concert alongside Sherbet vocalist Daryl Braithwaite, but said that she looks forward to returning again later this year to open the first stage of the Olivia Newton-John Cancer and Wellness Centre.
She said of the project at the Austin Hospital: "I'm really proud that's going to happen."
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Watch Olivia Newton-John in the trailer for A Few Best Men below: