A conservative young man has wound up his life before it was unreeled. We expect old men to be conservative, but when a nation’s young men are conservatives, its funeral bell is already rung.

Henry Ward Beecher (1813-1887) American clergyman and orator

Life Thoughts (1858) [ed. Proctor]
    (Source)

This was more succinctly summarized in Proverbs from Plymouth Pulpit, "Political" (1887) [ed. William Drysdale]:

When a nation’s young men are conservatives, its funeral bell is already rung.