Sabor de bien que es finito
Lo más que puede llegar
Es cansar el apetito
Y estragar el paladar.
Y así, por toda dulzura
Nunca yo me perderé,
Sino por un no sé qué
Que se halla por ventura.
From St. Juan de la Cruz, "Glosa a lo Divino". A rough, quick translation:
The taste of finite good:
the most it can give
is the tiring of the appetite
and the ruining of the palate.
And so even for all sweetness
I will never lose myself,
but for an I-know-not-what
that fortunately is found.
But "por ventura" as a poetic expression is somewhat tricky; it can mean fortunately, happily, by chance, as luck would have it, and so forth. "Fortunately" and "happily" with their association with chance (fortune in the one case and happenstance in the other) perhaps do the best.
