The Sweden striker scored his third goal in as many games during Liverpool's 2-0 win over Ipswich Town on Friday, matching his entire Premier League goal tally from an injury-hit campaign last season.
Liverpool remain unbeaten under manager Andoni Iraola, and Isak believes they must build on their strong start as the schedule becomes more demanding.
"I feel good," Isak told Sky Sports News.
"Obviously, I would have preferred if we had won all of our three games. But we won the last one and we have got to keep going like that."
The striker believes Liverpool can take confidence from the Ipswich performance into their next two matches.
"We've got to use the energy from that game and use it to put in another good performance," Isak said.
Liverpool now turn their attention to the Champions League, with Atletico Madrid visiting Anfield on Wednesday.
The Reds will then return to Premier League action on Saturday when Fulham travel to Anfield, with Isak looking to continue his impressive scoring form.
Borussia Dortmund defeated Villarreal 3-2 in their UEFA Champions League opening clash at the Signal Iduna Park on Tuesday evening after a Serhou Guirassy double strike.
Liverpool head into their Champions League opener against Atletico Madrid with manager Andoni Iraola facing an early test of his squad management.
Aston Villa scored three goals in the first half and then held on to beat Club Brugge 3-2 in their UEFA Champions League opener in Belgium on Tuesday.
Harry Kane, Lamine Yamal and Kylian Mbappe headline the 30-player shortlist for the 2026 Ballon d'Or, with the winner to be announced at the ceremony in London on October 26.
