Italian's often called the language of love, and it's full of phrases and quotes that are testaments to the importance of love. "Amor non conosce travaglio" means "love never tires," and would be a good choice to honor eternal love. "Amore è cierco" is the Italian phrase that's equivalent to the English expression, "love is blind." "Chi ha l’amor nel petto, ha lo sprone a’fianchi" is long, but has a distinct and powerful meaning: "one who has love in one's chest has spurs at one's side." Finally, "chi ama, crede" is a simple, strong statement: "he who loves, trusts."
Philosophical or thoughtful phrases are rampant in Italian, and would go well for a tattoo to remind you of values or beliefs. "Del male non fare e paura non avere" means "commit no evil, and have no fear." "Cui niente sa, di niente dubita" means "one who knows nothing, doubts nothing." "Cui niente sa, di niente dubita" is loosely translated as "there isn't a rose without thorns," similar to the common English phrase.
"Aiutati che Dio ti aiuta" is Italian for "God helps those who help themselves." It would be good for a tattoo about determination and perseverance. "Breve orazione penetra," or "God hears short prayers," would be another short, religiously-themed Italian phrase for a tattoo. "Dio volendo lo faro" means "If God wills it, so do I," while "ognuno per sè e Dio per tutti" means "every man for himself and God for all." All of these phrases would work, both as individual phrases, or in conjunction with religious imagery.