Graham Potter felt his Swansea City side had paid the price for not being good enough in either penalty area during their 3-2 defeat to Hull City.
The Swans had raced into an early lead through Wilfried Bony's fine strike and controlled the majority of the opening 35 minutes.
They had chances to extend their lead, although they also needed Erwin Mulder to make a fine penalty save to prevent Jarrod Bowen levelling from the spot.
But Swansea were ultimately undone by three goals in 10 minutes from their hosts as Bowen made amends for his earlier miss with a brace either side of Tommy Elphick's header.
Bersant Celina pulled a goal back late in, with Oli McBurnie's header coming agonisingly close to snatching a point, as the Swans suffered a seventh defeat in their last eight visits to Humberside.
"It's a lesson for us because our overall game management can be better," said Potter.
"In the end we are really disappointed with the result.
"The boys are honest they know we need to do better in terms of how we defend the box and how we are when we are attacking to limit the opportunity for teams transitioning on us.
"Then we need to finish better. You can talk all you want but the game is about what happens in the boxes and they scored three goals and we scored two.
"It is a sore one for us. I cannot sit here and say everything was bad, we did a lot of things well but we were not good enough.
"If we score that second goal and kill it off maybe the atmosphere changes here.
"But we didn't and while it is 1-0 it does not take much and the ball is in your box and in the back of your net.
"The reality is we were not good enough in both boxes."