Yes, Wessex, that's the word "half-heartedness":
Lukewarm: halfhearted ("tibio" in Spanish, hence Our Lord's words "los vomitare de mi boca"). (Lacking in real conviction, not wholly committed to a cause or belief). Done.
Coward: fainthearted. Can become brave (very brave!) given the proper detonator. (timid, irresolute, impulsive in any crisis). Our hope.