Lewington's side, who sit in a healthy top half position, played with hustle and bustle all afternoon but, as Danny Webber will testify, lacked an end product.
The Watford boss agrees, and suggested his side simply had the proverbial 'bad day at the office'.
"There are ways of losing a football match and I'm not upset at all with the players' attitude or approach to their work," said Lewington, speaking after the game.
"We had a go - it just wasn't our day. It was a really even game which always looked as if one goal would decide it.
"Losing is horrible but just as we've kept our feet on the floor during our unbeaten run, so we'll not let this defeat set us back.
"The good habits were there, the tempo of the game was decent even if the quality of our play sometimes let us down a bit."
Following today's defeat the Hornets will be hoping to get something out of their tricky home game against Wigan on Tursday, and with sharper shooting maybe they will.