Literal translation
The if spoils the shrub
Meaning
don't count too much on how things will turn out
Explanation
This saying warns against building too much on suppositions about the future, which spoil plans just as too much calculation spoils a young plant before it has even grown. The se in the text is the hypothetical if, personified as an agent that damages (gasto) the shrub (aubret), meaning a project still fragile, still a seedling. Building on conjecture, on a cascade of ifs, amounts to mishandling a sprout before it has had the chance to become a tree: the future gets killed by trying too hard to foresee it, or by resting it on uncertain conditions. The expression is close in spirit to sayings that mock reasoning built on unverifiable hypotheses, the kind that would bottle up a whole city given enough ifs. The register is common and sententious, used to cut short a discussion drifting into speculation, at the expense of fact.