Michail Antonio's 85th minute winner gave the home side all three points, though the Cherries boss felt that his side could have picked up a winner of their own in the second half.
"It's a tough afternoon," the manager told BBC Radio Solent.
"With 20 minutes to go I felt we could potentially be on for three points, let alone one.
"We were much improved in the second half and looked dangerous. They hadn't really got near our goal, so to end up losing the game is a bitter pill to swallow.
"I think we will look back and kick ourselves that we didn't come away with something. That's got to be the ultimate disappointment."
Harry Arter was given his marching orders by Craig Pawson on 77 minutes after committing a second bookable offence.
And Howe earmarked that incident as having a huge bearing on the outcome of the match.
"We need to keep our discipline and stay in the moment," he continued.
"We need to keep our cool and we didn't, that has cost us today. It's a disappointing moment for us - the red card has had a huge bearing on the result.
"It's certainly something we need to learn from quickly. We pride ourselves on our discipline and making sure that we are smart and savvy, but in that moment we were not."