allow nature to take its course
To let events develop and conclude naturally, i.e., as they would without outside intervention, help, or interference. The phrase can refer literally to nature or figuratively to manmade situations or events. Though I know people are eager to help those affected by the earthquake, unfortunately we have to allow nature to take its course before anything can be done. We've done as much preparation for the election as we can; we just have to allow nature to take her course tomorrow.