To let events develop and conclude naturally, i.e., as they would without outside intervention, help, or interference. The phrase can refer to nature literally, or figuratively to manmade situations or events. If we were to let nature take its course and stop maintaining this lot, it would look like the rest of the forest in months.
not try to change or influence a situation: As a parent, sometimes you need to sit back and let nature take its course; if you try to stop your child from making any mistakes it can be more damaging in the end.