Boro remain unbeaten this season but won at home for only the second time, and the first on a Saturday, when Greg Tansey's free-kick sank Scunthorpe 1-0 at the weekend.
"I was a little bit frustrated because I know what quality we have, and what we're capable of," said Smith.
"There was edginess too, because we want to win so badly at home, given our away form.
"We want to get those results in front of our own fans and not just on the road. And when you're not quite as assertive as I know the players can be, you start to get a little bit twitchy.
"It was the first Saturday afternoon game here where we've kept a clean sheet and won the game, so it was really good afternoon for us."