The Nationals have made a habit of following up consecutive losses with consecutive wins.
I just looked back through this season, and only twice on the entire season did the Nats drop two or more in a row and not follow it up with 2 consecutive wins.
The first one happened after dropping 3 to the Marlins (May 29-31) then a W-L-W-W against the Braves for 2 (with a June 5 rainout) and then Mets (June 3-7)
The second happened after dropping 3 to the Barves (Sept 15-17) then a W-L-W against the Dodgers (Sept 19-21)
At no point did the Nats fail to follow 2 losses with 2 wins.
This is what helped them win the division and best record in baseball, and this is what may help them win the NLDS. It all comes down to being that team with the spark we saw all summer.