In English : Without knowing the source-language, I think French version should have been formulated in another way, because it isn't current, particulary for the equivalence meant by verb "être", to see at one hand a subject and a verb at singular form, then at the other hand a complement which is at its plural form.
So that one needs a less literal translation, eg reading : "en amour on ne compte pas" , or "on ne calcule pas".
But I may be wrong about exact meaning of the source-text, and I would need an English version to evaluate this short text more easily...