England match-winner Jacks proud, confident heading into Super Eights
Jacks scored his maiden T20 international fifty off an England World Cup record 21 balls to guide his side to their highest total of the tournament, 202-7.
"To make a mark on the game is something I haven't done enough of in my T20 career," Jacks added.
"There have been a lot of games and many tours where I've not been living up to my own expectations and not doing well for the team.
"To have a match-winning contribution, I'm obviously proud of that."
He added that England were confident they could go on and win the T20 World Cup despite some stuttering performances in the group stage.
Harry Brook's side were given a scare by T20 World Cup debutants Italy on Monday.
That came after beating Nepal in a last-ball thriller at Mumbai's Wankhede stadium in their opening game.
"Winning like that can only be good for you," Jacks told reporters at Eden Gardens.
"We don't want it to be that close and feel those nerves.
"But, going forward, it's more experience and we can never have enough of that."
England also lost to the West Indies at the same venue and wobbled before completing a modest chase against Scotland on Saturday in Kolkata.
But Jacks said coming through some tough battles was a good sign as they now head down to Sri Lanka where they will play all their Super Eight matches.
England won a T20 series there 3-0 against the co-hosts Sri Lanka before the T20 World Cup.
"Going back to Sri Lanka, we feel confident there," he said.
"That experience is good for us.
"We've obviously done it the hard way, we've not made it easy. But the most important thing is we are on to the Super 8s."