[spodek]

Nelson Mandela spent 27 years in jail before becoming president and father of a nation.

While "only" 4 years, Muhammad Ali sacrificed what would have been the prime of his boxing career as a conscientious objector. He was famous as a great athlete before, but transcended it after.

Alexander Calder was an engineer for about ten years before becoming one of the great artists of the 20th century.

Many other examples.