Before abandoning some effort already underway, consider how much resources (time, money, political capital) you have already invested.
Don't change horses in the middle of the stream.
There ain't no such thing as a free lunch.
See Sunk costs for the economic critique of this rule. Your decision to continue a course of action should only depend on the current Value of doing so, and not on how much you have invested. Yet in a world that is pathologically unpredictable, nobody knows what the future value will be (least of all economists.) Valuable results usually only come from effort — though our efforts may be wasted, given that we cannot know the true value, we use the amount we have invested as a proxy.