Please help, I need an explanation about "the decline of Mr.Morel" in the novel Sons and Lovers.

Walter Morel is Gertrude's husband and a coal miner. He is rugged, handsome, sensuous, and very practical, deriving much of his joy in life from working and being with his fellow miners. Although he pledges not to drink, he begins to after the birth of their first child. The Morels quarrel regularly, often over Walter's drinking. Gertrude grows to loathe not only Walter's drinking but his crude and unsophisticated behavior as well, and she enlists her children in hating their father. After his wife dies, he becomes a broken man, full of regret and fear.