Nichiren Daishonin said:
“There are two types of faiths in the Lotus Sutra:
One is like fire, while the other is like water.
When the former hears the teachings, their passion quickly flares up like a fire, but as time goes on, they burn out and lose their faith. When the latter hears the teachings, they have faith like water which means to believe continuously without giving up.”
Unbreakable Happiness 