"It is a time when a man reaches the peak of a mountain range. He looks back over where he has come from and forward to what lies ahead. He also looks at himself and asks, “Now that I’ve climbed the mountain, am I an different for it? Do I feel fulfilled? Have I achieved what I want to achieve?" - Jim Conway, Men in Mid Life Crisis.
By this point in life, it is not uncommon for a man to feel as if he has no deep and satisfying relationships with other men. His friendships may all be more work-related dissatisfying and not lend themselves to inner opening. He may yearn for or idealize “the good old days” of his youth where he had a broad and satisfying range of relationships. As if this was not enough, society through the media proclaims the message to him that he is over the hill as youth is heralded and aging is portrayed as the ultimate curse.
(The above was taken from a thesis I wrote in the early 1980's as part of my course work for a Master's Degree.)