Third-flight leaders Cherries suffered only their second League One defeat since Howe’s Dean Court return following a below-par performance at Preston North End.
One-time Cherries transfer target Stuart Beavon fired Preston into a 19th-minute lead when he drilled low past Shwan Jalal from 20 yards.
Cherries’ failure to clear a deep free-kick allowed North End defender Bailey Wright to double the advantage when he bundled home 31 minutes.
Two close-range headers from Steve Cook and Shaun MacDonald flew over the crossbar as Cherries improved late on but their attempts came to nothing as Preston claimed a deserved win.
Howe said: “We weren’t at our best – there is no doubting that. We were second best which is really difficult for me to say because it hadn’t happened yet. This was the first time.
“We were slow out of the traps, we conceded two poor goals, we never really had any concerted pressure on their goal and I think we have to try to forget this as quickly as possible.
“Of course, learn from it and analyse it, which we will, but we have some massive games coming up which will define our season.”
Asked if he could pinpoint a reason for Cherries’ slow start, Howe replied: “I think you can look for a combination of factors. We have had a lot of travelling, a lot of games and we have got some tired bodies.
“It was a really poor pitch again. It was the same for both teams but we didn’t react very well to it.
“But we didn’t play our best. We are the first to admit that and are not looking for excuses.
“We have to retain our long-term vision, see where we are in the table and collect all the positives from that and look forward because looking back is going to do us no good now.”
Howe decided to hand a debut to loan recruit Marcos Painter with Cherries keen to allow Matt Ritchie to play in his preferred role on the right wing.
The Cherries manager was forced into an early reshuffle with Marc Pugh still feeling unwell following illness in the week, and he tinkered with his formation after the break in a bid to get a positive result.
Howe added: “We tried to try to get a foothold in the game.
“We were 4-4-2 with Brett Pitman just dropping in early on and we weren’t getting to grips with their midfield.
“We changed personnel – Marc Pugh was struggling through illness, he didn’t feel good during the game so we had to make that decision.
“In the second half, we tried to change again to try to get some momentum and try to get up the pitch.
“But I don’t think it was tactical today, there were bigger things that proved our downfall.”
Cherries' defeat, coupled with wins for rivals Sheffield United and Yeovil Town, saw both clubs close to within a point of the Dorset outfit.