Sri Lanka lost their first three matches in the series and are trying to become the first team in the history of the annual tournament, which started in 1979-80, to qualify for the finals after such a poor start.
Sri Lanka thrashed World Cup champions Australia by 79 runs in Sydney on January 9, scoring 343 for five, the highest tally ever recorded against Australia.
The massive total against Australia came just two days after the tourists were bowled out for 65 in a one-day game against Australia A in Adelaide.
"What we discussed was that we need to play our natural game, especially myself," said Jayasuriya, who made 122 from 105 balls and shared an opening stand of 237 with Marvan Atapattu (101).
"I need to go and play my own shots. You can't hang around," Jayasuriya told reporters in Sydney on Sunday.
"What we needed was one win to change the whole thing and we did that the other night.
"It gives you a lot of confidence (to beat Australia) because that's the best team."
Sri Lanka need to beat England on Monday to strengthen their hopes of reaching the finals.
Australia have won four of their five matches and lead the series with 22 points with England on 13 and Sri Lanka on seven.
Jayasuriya said defending champions Australia and hosts South Africa were worthy World Cup favourites for the tournament starting in southern Africa next month. "(But) anything can happen," he added.
