Getting ahead of your competition will win you a fantasy football championship if you're cautiously aggressive.
For instance, if you're undefeated or 4-1 with a solid-to-strong running back stable that includes David Johnson, this might be the time to make a move. Even though Johnson is coming off another top-10 performance, a lot of his value is tied to touchdowns. It makes sense in the long run to turn him into a more stable asset on a better, contending team (or into assets on contending teams).
If you've been streaming quarterbacks over the first month of the 2018 season, one extra step is to find someone who has more than just one good matchup over the next few weeks.