A、Because its definition is complex. B、Because there are too many landmarks. C、Because it is a journey that never ends. D、Becaus

There are two basic ways to see growth: one as a product, the other as a process. People have generally viewed personal growth as an external result or product that can easily be identified and measured.
    (26)By contrast, the process of personal growth is much more difficult to determine, since by definition it is a journey and not the specific landmarks along the way. The process is not the road itself, but rather the attitudes and feelings people have, their caution or courage, as they encounter new experiences and unexpected obstacles. In this process, the journey never really ends; there are always new ways to experience the world, new ideas to try new challenges to accept.
     In order to grow, to travel new roads, people need to have a willingness to take risks, to confront the unknown, and to accept the possibility that they may "fail" at first. How we see ourselves as we try a new way of being is essential to our ability to grow. (27)Do we perceive ourselves as quick and curious? If so, then we tend to make more chances and to be more open to unfamiliar experiences. Do we think we’re slow to adapt to change or that we’re not smart enough to cope with a new challenge? Then we are likely to take a more passive role or not try at all.
    (28)These feelings of insecurity and self-doubt are both unavoidable and necessary if we are to change and grow. If we do not confront and overcome these internal fears and doubts, if we protect ourselves too much, then we cease to grow. We become trapped inside a shell of our own making.