Nichiren Daishonin states in “Reply to Matsuno”:
There are many baby fish, but only a few mature to become full-grown fish. Although the mango tree blooms proliferously, few of its flowers turn into fruit. The same is true for humans. There are many who resolve to attain enlightenment, but only a few refrain from slackening in their practice and manage to achieve the true way. The aspiration of common mortals to attain enlightenment is often hampered by evil karmic influences and is easily affected by various conditions and circumstances. There are many heavily armoured warriors, but only a few among them are fearless when they go into battle.