Generally the Sanskrit word ’vajra’ means indestructible like a diamond and powerful like a thunderbolt. In the context of Secret Mantra it can mean the indivisibility of method and wisdom, omniscient wisdom or spontaneous great bliss.
Moral discipline is most important for everybody in order to prevent future problems for oneself and for others. It makes us pure because it makes our actions pure.
Buddha identified the six root delusions that poison our mind as follows:
(1) attachment, (2) anger, (3) pride, (4) ignorance, (5) deluded doubt and (6) deluded view.
Shantideva: "Although my enemies of hatred, attachment and so forth have neither weapons, legs nor arms, still they harm and torture me and treat me like a slave."