Make every possible effort for the sake of your next life. What is most important is that, by chanting Nam-myoho-renge-kyo alone, you can attain Buddhahood. It will no doubt depend on the strength of your faith. To have faith is the basis of Buddhism.

The Writings of Nichiren Daishonin, page 832
The Real Aspect of the Gohonzon
Written to Nichinyo on August 23, 1277