Martin Kelly's first half injury time goal settled Sunday's fifth round tie at the Lane.
But as Nabil says, there is no time to dwell on what was only our sixth defeat in 38 matches in all competitions this season and first in the last 10.
"We all know how important the FA Cup is and we're all disappointed but we have to start again and concentrate on Fiorentina," said the midfielder. "We have to be focused, determined and bounce back.
"The players didn’t say a lot afterwards. Everyone was upset and sad. That’s what you expect when you lose. We’d all rather be celebrating a win but it wasn’t to be."
Below: The chalkboard shows Nabil's distribution and defensive work against Palace
Chances came and went against Palace including a Dele Alli shot that hit both posts. Dele had another header cleared off the line, Wayne Hennessey denied Harry Kane and Christian Eriksen and when both Harry and Josh Onomah both failed to turn home Dele's cross, you just felt it wasn't our day.
"We dominated the game, especially in the first half, created a lot of chances, couldn’t finish, conceded and couldn’t break them down, that just about sums it up," added Nabil, who made only his fifth start of the season.
"Sometimes you have those days when it just doesn’t go right. We all saw the ball from Dele hit both posts and go across the line in the first half. We gave everything but it didn’t want to go in for us."