Those who are weak don't fight.
Those who are stronger might fight
for an hour.
Those who are stronger still might fight
for many years.
The strongest fight
their whole life.
They are the indispensable ones.

As quoted in Democracy Unbound : Progressive Challenges to the Two Party System (1997) by David Reynolds; also quoted by Cuban musician and poet Silvio Rodríguez before his song "Sueño con serpientes". | Also quoted by Eduardo Galeano (Uruguayan writer) to describe Nestor Kirchner as he received the notice of his death.

There are men who struggle for a day and they are good. There are men who struggle for a year and they are better. There are men who struggle many years, and they are better still. But there are those who struggle all their lives: These are the indispensable ones.