There is one fundamental thing that has changed in our societies since 1950: life has got longer. Over the last few generations, 20 or 30 years have been added to the duration of our lives. But after the age of 50, human beings experience a kind of suspension: no longer young, not really old, they are, as it were, weightless. It is a reprieve that leaves life open like a swinging door. The increase in life expectancy is a tremendous step forward that upsets everything: relations between generations, patterns of family life, the very meaning of our identity and our destiny. This reprieve is both exciting and frightening. The deadlines are getting shorter, the possibilities are shrinking, but there are still discoveries, surprises and upsetting love affairs. Time has become a paradoxical ally: instead of killing us, it carries us forward. What to do with this ambiguous gift? Is it only a question of living longer or living more intensely? To continue along the same path or to branch out and start again? What about remarriage, a new career? How to avoid the weariness of living, the melancholy of the twilight years, how to get through great joys and great pains? Nourished by both reflections and statistics, drawing on the sources of literature, the arts and history, this book proposes a philosophy of longevity based not on resignation but on resolution. In short, an art of living this life to the full. Is there not a profound joy in being alive at the age when our ancestors already had one foot in the grave?  This book is dedicated to all those who dream of a new spring in the autumn of life, and want to put off winter as long as they can.