If you put a buzzard  in a pen  six to eight feet square and entirely open at the top, the bird, in spite of its ability to fly, will be a prisoner. The reason is that a buzzard always begins a flight from the ground with a run of ten to twelve feet. Without space to run, it will not even attempt to fly, but remain a prisoner for life in a small prison with no top. The ordinary bat that flies around at night, a remarkably nimble creature in the air, cannot take off from a level place. If it is placed on the floor or flat ground, all it can do is to _ about helplessly and, no doubt, painfully,until it reaches some slight height from which it can throw itself into the air. Then, at once, it takes off like a flash. A bumblebee  , if dropped into an open tumbler , will be there until it dies, unless it is taken out. It never sees the means of escape at the top, but insists on trying to find some way out through the sides near the bottom. It will seek a way where none exists until it completely destroys itself. In many ways, there are lots of people like the buzzard, the bat and the bumblebee. They are struggling about with all their problems and frustrations, not realizing that the answer is right there above them. Why does a buzzard choose to stay in a pen?
Because it is safe to live there. Because it gets used to living there. Because it cannot take off within an limited area. Because it lost its ability to fly.