The manner of the defeat to Bohemians was a "bitter pill" to swallow for Shelbourne head coach Ian Morris and his charges.
Newly-promoted Shels slipped to a 2-0 defeat against their Dublin rivals in the SSE Airtricity League Premier Division on Friday night after second-half goals from Andre Wright and Danny Mandroiu.
"It's a bitter one to take but you can't give away poor goals and not take chances - that's the name of the game," Morris told RTÉ Sport's Tony O'Donoghue at Dalymount Park.
"I thought we were unlucky not to go in at half-time leading. We came out in the second half and [Aaron Dobbs] has had a good chance to put us 1-0 up, again [we] don't take it, and then we just give away two sloppy goals which then flips the game.
"You can't go down one end and not take your chances and give away silly goals at the other end."
He added that "what makes it more frustrating" is not dealing with Bohs' headers in their box given the aerial ability his own squad possesses.
"It's a tough one to take with the chances we created," Morris added, admitting that the defending "wasn't good enough".
The result leaves Shelbourne fifth with two wins and two losses from four matches, while Bohemians are up to third after five games with three wins.
Bohs manager Keith Long admitted it was "a fair assessment" to say his side were second best in the first half and described it as a "really disappointing performance" in that period of the game.
"Shelbourne were sharper, they were quicker, they had a lot more bite in the tackle, they won a lot more collisions, first ball and second ball," he said.
"Chances were at a premium. There weren't a huge amount of chances at either end. But we weren't happy with our first half display.
"Second half, we came out of the traps a little bit more to play on the front foot. Our distribution from our goalkeeper was a lot quicker.
"We got Danny Grant and Kris Twardek into the game. Danny Mandroiu came alive and Andre Wright got a great goal from a cross; Danny Grant good header back, cross from Kris Twardek and Andre takes his goal really well."
He also praised Mandroiu's "invention" and "clever play" for the second goal, adding that "Danny sees things that others can't".