Old age may bring an inability to concentrate, forgetfulness, inability to converse, to hear, to see. So the old person gets used to sitting in a chair daydreaming, vegetating, saying nothing. There is sometimes a lack of motive to live, too much idle time, and too much time for complaining. There may be a desire to travel but no means to do so. So there is a lack of significant things to do.
Old age brings future shock.
Old age finds itself out of phase with the younger generations of children and grandchildren. Therefore a dangerous trend can get started toward hypercriticism. The older believer may have stopped growing spiritually, or worse, may never have got started. There is, therefore, no edification, no occupation with Christ, no desire for the Word. There is a tendency to stagnate, to become jaded, to rely on the study done years before.