The Cherries fell to a 1-0 defeat on Sunday evening in the first Premier League game to be staged at the Olympic Stadium, coming undone in the final five minutes.
Speaking to BBC Sport after the match, Howe confessed that the dismissal of his key midfielder 77 minutes in ultimately cost his side a share of the spoils.
"It's a tough afternoon," he said. "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. We need to keep our discipline and stay in the moment. 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."
Bournemouth, still without a point this season, are back in action in midweek with a trip to Morecambe in the EFL Cup.