If it is true that there are as many minds as there are heads, then there are as many kinds of love as there are hearts. – Anna Karenina
After he first knew himself to be in love, and even well after he had sunk into tortured decades of sleep, Vincent held on to that mixture of uncertainty and elation and hunger that came whenever he thought of Lucrecia and had nearly overwhelmed him every time he had seen her beloved face. The lurch in his stomach, the shallow, irregular breaths – he wouldn't trade the memory of them for anything. Amidst the chaos and unrequited everything of his relationship, these feelings and his utter devotion to them were constants. Only for Lucrecia, he vowed.
He liked to think this love sustained him. But he knows better now. One cannot sustain something that isn't alive. Vincent may have had a pulse, but he wasn't the type who let anyone get close enough to check for it. If anyone was destined to be a Turk, it was Mr. Valentine: he of the steady aim and unfaltering hand and complete disregard for human life. How could he value it when he knew nothing of it?
Lucrecia, or at least the love she inspired, woke him up from the empty, ordered existence he called his own. Otherwise, he might have gone to his grave as the perfect ShinRa employee, his unquestioning obedience not a sign of loyalty as much as an absence of convictions. He had never known such deep, mind-enslaving emotion before her. It drove him to make sacrifices that he had never considered, gave him a shred of empathy. It warped him, nearly destroyed him.
But, it did wake him. He will not belittle the memory of his first love by not recognizing that.
Now he has the steadfast love of a Wutaian princess, as he is so fond of calling her. She is all that is good and true and young and wise and hopeful. So much hope: for herself, for him, for all of them. A princess in every sense that truly matters.
Upon returning to the world of the living, he noted the stirrings of his heart that the young Shinobi generated with her unflagging optimism and fearless attachment to him, but did not move to stifle them. He felt safe and called himself faithful, as they were nothing like what he felt for Lucrecia. That was the only way to love, after all, wasn't it? These invigorated thumps in his chest were simply the creaking of machinery lain dormant for too long. Nothing to be alarmed about.
Even to this day, when he looks at Yuffie, his heart expands in his chest and his pupils automatically dilate with happiness, drowning out some of the unnatural red of his eyes. He is a new man, capable of better things, because of her. This love does more than sustain: it enriches, it enlivens, it saves him. It is nothing like Lucrecia.
Of all of his blessings, he thinks perhaps that is the best.