When you take a look at the top players in the world on the ATP (i.e. - Nadal, Federer, Djokovic, Murray) there are numerous things they do better than the rest of the field, but one thing that sticks out to me, is their innate ability to turn defense into offense. There are a couple different ways to do this, best portrayed by the top two players in the world, in Nadal and Federer. Nadal has an uncanny ability to hit a blistering winner on the dead run off of either wing, which we have seen multiple times in some of the Federer-Nadal classics, like the 2008 Wimbledon and 2009 Australian Open Finals.
Federer and Murray are more capable of using their finesse and touch while on the run, by slicing the ball low and away from their opponents. Either way, after Nadals’ huge shots on the run, or Federer's low, well placed slice on the move, puts them from a defensive position into an offensive position. Work on being able to be effective on the run and your game will improve.