Following their 157-run defeat at the weekend, England bounced back to bowl Sri Lanka out for 67, before surpassing the total in 12.1 overs.
The captain told Sky Sports News: "We did discuss it, of course, but it was a really strange game. The way we performed at The Oval to then perform like we did there was really strange.
"But the lads came out firing, desperate to prove a point today, and we did that. We didn't quite get set straight away so the way we held our nerve and kept building pressure, and then when we got the chance [Chris Jordan] really hit the mark."
The two sides play again at Lord's on Saturday.