"at thirty strength" (Avot 5:25)

“It happens often in the twenty-ninth year of a life that all the forces that have been engaged through the years of childhood, adolescence and youth in confused and ferocious combat range themselves in ordered ranks (and during which) the straight and narrow gateway of maturity, and life which was all uproar and confusion narrows down to form and purpose, and we exchange a great dim possibility for a small hard reality. 

Also in our American life where there is no coercion in custom and it is our right to change our vocation so often as we have desire and opportunity, it is a common experience that our youth extends through the whole first twenty-nine years of our life and it is not till we reach thirty that we find at last that vocation for which we feel ourselves fit and to which we willingly devote continued labor.” 

Gertrude Stein, Fernhurst, p. 29