Erikson describes the issue of “integrity versus despair and disgust” as a basic task in mature age,…” the acceptance of one’s own ….life cycle and of the people who have become significant to it as something that had to be and that, by necessity, permitted of no substitutions…..”

Page 121,

The limits of creativity

Each of us has our own timetable for establishing a home, for being ready to marry and have children, for learning and carrying on a profession. A mathematician’s most creative contribution may come when he is in his twenties, a surgeon’s in his forties, and a good many artists’ and philosophers’ when they are in their sixties and even later. For most people, however, a time comes sooner or later, and usually during middle life, when they perceive with clarity the limits of their past and especially of what they can accomplish in the future, and they have to learn to accept themselves within such limits. Here again, one must come to accept that other people’s achievements will at some point surpass one’s own.

P 126, Internal World and External Reality, Otto Kernberg