Matt Shepherd scored all of Cornwall's points as they edged to a 22-16 victory at Kent in the County Championship.
Graham Dawe's side now have two wins from two in the competition and will reach the Twickenham final if beat Hertfordshire at home this weekend.
"I think our game management was really outstanding at times," captain Kyle Marriott told BBC Radio Cornwall.
"After our result last week some people thought this would be easier for us, but we certainly never thought that."
Cornwall now face a winner-takes-all match against pool leaders Hertfordshire.
They are looking to reach the Twickenham final for the third year in a row and visit Kent in their next game in the group.
"Having someone like Matt Shepherd, who can kick the points from most areas in their half, was really useful," added Marriott.
"We're chuffed to bits and hoping for a big crowd down at Redruth."
In the last two years, Cornwall have missed out on lifting the trophy by losing to Lancashire, who have dominated the competition.
They beat Gloucestershire 27-8 at Cinderford in the first game of their County Championship campaign.
"It shows that we can come together when we're against it and the odds are stacked against us," Shepherd added.
"Everyone's going to be fighting for their lives next week."