Japan's Crown Princess Masako says she feels "insecure" about becoming empress in April, but will do her best to serve the people of Japan.
Masako Owada will become empress when her husband, Crown Prince Naruhito, succeeds his father Emperor Akihito.
Emperor Akihito, 84, is abdicating next year because of his age and health.
The princess, who has suffered from a stress-related disorder for many years, says she is slowly recovering and will try to perform more royal duties.
Princess Masako was educated at Harvard and Oxford, and had a promising career as a diplomat before her marriage in 1993, the BBC's Asia analyst Michael Bristow reports.
However, she has struggled to cope with royal life and Japan's notoriously conservative imperial household, our correspondent adds.
The princess made the comments in a statement marking her 55th birthday.
"Giving thought to the days ahead, I sometimes feel insecure about the extent to which I will be able to be of service to people," she said. "But I will strive to do my best so that I can contribute to their happiness."
She said that she was "filled with deep emotions" and felt "nostalgic" that this was the last year before Emperor Akihito abdicated.
Princess Masako's doctors say she suffers from "adjustment disorder", a condition caused by stress, that is often linked to depression or anxiety.
In Sunday's statement, she said that her health was improving slowly, adding: "I am happy as I can now perform more official duties than before, little by little."
Her doctors emphasised, in a separate statement, that it was important that the princess be allowed to continue her treatment and not be subjected to too much pressure.
The princess "is still on the recovery track and there are ups and downs to her condition", they said.
