Sam Vokes admits Wales must remain mentally strong after reaching the quarter-finals of Euro 2016.
Wales edged past Northern Ireland on Saturday to reach the last eight after winning a tense clash in Paris 1-0.
Northern Ireland held their own for most of the match only to be undone by a Gareth McAuley own goal during the closing 15 minutes of the game.
They now face either Hungary or Belgium next Friday and Vokes said: "They're all big games and the next one is the quarters. You never know what could happen if you get a result there.
"Every game is different and it's tough to go into every game with the same mentality.
"But you've got to keep grinding out results, whether we're playing 100 per cent as we were against Russia or against Northern Ireland when we were off it a bit."
As for the win over Northern Ireland, the Burnley striker added: "With it being a British derby, it was always going to be difficult to break them down and I thought they were brilliant in the way they went about it.
"But Gareth's ball across the box was the difference and to nick it at the end was a great feeling.
"They are special moments and that's what this journey's been all about. We build on that and hopefully get another one next week."