The answer is gain and loss.
To complete the sentence: Middle adulthood is generally a unique developmental period characterized by gain and loss.
Middle adulthood is a rather long period of the lifespan between the ages of 40 to perhaps 65.
Most midlife adults are engaging in many developmental tasks and they may be launching their children into lives of their own and adjusting to life after their children have left. Most of them-midlife adults, experience good health but, changes in vision, becoming near or far sighted are very common. Midlife adults also become more flexible and less rigid in decision making.