As her 70th birthday approached three years ago, actress and philanthropist Jane Fonda discovered she was the happiest she’d ever been in her life.

Why?

She didn’t know. What she did know was that she hadn’t expected to be so happy.

Was this true for most older folk?

In her quest to answer that question and inspire others toward a more fulfilling life, Fonda found within her a second memoir, "Prime Time: Love, Health, Sex, Friendship, Spirit:  Making the most of all your life."

And she isn't done, she said last week.

"I am working on three new books on adolescent sexuality, one for middle school teens, one for high schoolers and one for the parents of teens," said Fonda. "This grows out of my work with GCAPP, the Georgia Campaign for Adolescent Pregnancy Prevention."

Meanwhile, Fonda answered a few questions about "Prime Time," which is being released today.

Q. Why after "My Life So Far," did you feel you had more to say?

A. "My Life So Far" is a memoir. "Prime Time" has a lot of very personal things in it, but it is an exploration of the life cycle, especially the last three decades...what I call the Third Act.

Q. Why do you think more people are happier in the second half of life than before?

A. An extensive study of 350,000 Americans from the very young to the very old showed that after age 50, people tend to become happier, less hostile, less stressed. This is true across the board, regardless of gender, marital status, etc. Obviously mental and physical disease, depression can mitigate against this, but this upswing in well-being is true for the majority.

Scientists postulate on the reasons: Older people have a long backward perspective. We've been there, done that, and survived. "This too shall pass" is a concept that is easier for older people to understand than it is for younger ones. We tend to see commonalities rather than differences. We know what we need and what we can let go of. We may lose eyesight, but we gain insight. All these things are certainly true for me and for the older people I interviewed.

Q. What is it about the years between 45 and 50 that leads to discovering who you really are or as you put it "were meant to be"?

A. Well, I am not sure the years between 45 and 50 are the years of self-discovery. They can be...or not. I think that for many -- not all, but many -- women they are difficult years as we enter perimenopause and then menopause and wonder who we are becoming. We can feel as though we are being broken when, if we pay attention, we are being broken open. I write a lot about this. But I do know that the third act--which, as I see it, begins at 60 -- can be the time when we become who we were always meant to be.

Q. What’s the key to making the most of your life?

A. Making the most of your life, I believe, has to do with understanding who you were as a younger person, who your parents and grandparents were, why they were the way they were. You may find that if things didn't go as they should have, it had nothing to do with you. You can discover who you were independent of them, and you gain clarity about what you can do in the years to become you were meant to be. Living with intention, consciousness...these are important.

Q. What about sex?

A. Many boomers and seniors have closed the door on the sexual parts of their lives, and that is fine. There is no right way to live these later years. For those who want to remain sexual, however, it is important to understand the age-related changes that happen to our bodies that can effect sexual activity and how to manage those changes. The fact is, sensuality and intimacy can be more profound now than ever before.

Q. And how do we get the most out of  love?

A. Because of many factors, hormonal changes in particular, men and women become more alike. Women's testosterone levels rise in relation to their estrogen and men's estrogen rises in relation to their testosterone. Men can grow more nurturing, loving, women more assertive. The results can be glorious. Women understand themselves and their needs more and are less afraid of asking for what they need. Intimacy and love require self-revelation and this becomes easier when you know who you are.