To die in the service of one's lord is the greatest service a Samurai can render. No dishonor can go unavenged. Dishonor to lord or family is also dishonor to the Samurai. Mercy is not due the enemy. All debts, both vengeance and gratitude, are repaid.
Cowardice is dishonorable.
A samurai would rather kill himself than bring shame and disgrace to his family name and his lord. This was considered an act of true honor. A Um my Life and Death. Ready Wit my Talent. No Mind my Sword.