Don't consider or proclaim a problem solved until you are sure that it is completely, permanently resolved, as more issues might crop up before then. (To "halloo" means to shout or yell in a boisterous way, especially to catch someone's attention.) A: "Acquiring this account will solve all our financial worries." B: "Never halloo till you are out of the woods. If they pull out or can't pay us in time, we'll be just as screwed as we were before." A: "I'm confident that the treatment will eliminate the cancer very quickly." B: "Never halloo till you're out of the woods, Doc. That cancer could still spread to other parts of the body."