Sunderland did the double over the Toon, with Brian Brobbey scoring in the 90th minute for the 2-1 win.
Howe said: "Painful, tough afternoon for us. Positive start, I thought when we scored we would go on and dominate but we never capitalised on that momentum. The first half fizzed out and second half we were second best.
"I didn't like our performance. Technically we were poor. The defeat is harsh on us but we didn't play well enough."
On if the fixture pile-up played a part, Howe continued: "I'm reluctant to use that as an excuse. Logic would tell you yes, but we have to do better. We have to really look at ourselves and make sure we learn from all the mistakes we have made and we made a few today. This has happened before, it isn't a one off.
"We have some massive games to come. Week to week we are able to train and get that freshness back. We have had to learn a lot. It's going to need a lot of character to respond. We never give up, we always go for what we can."
On Malick Thiaw's disallowed goal, the manager added: "These are big momentum swingers for us. We wanted a second goal, we couldn't find it. Sunderland grew into the game.
"We needed to defend with our lives and defend better than we did."