|2015 World Championship|
|Venue: Crucible Theatre, Sheffield Dates: 18 April-4 May|
|Coverage: Watch live on BBC TV, HD, Red Button, Connected TV, online, tablets, mobiles and BBC Sport app.|
Mark Allen said his failure to secure victory when he was on top was the reason for his 13-11 World Championship second-round defeat by Barry Hawkins.
World number 12 Allen, 29, played some stunning snooker as he went 11-8 ahead.
But world number five Hawkins won five frames in a row to progress.
"I didn't do a lot wrong but, at the latter stages, you have to do a lot more right than I did," Antrim potter Allen told BBC Sport.
"The last session was frustrating. Barry did a good job and froze me out. Any chances I had were half-chances and the balls were awkward.
"Barry did very well and I was probably average. But it should have been over after the first 20 frames. I felt Barry was hanging on."
Allen led the 2013 runner-up 5-3 after Friday's first session at the Crucible Theatre and maintained the two-frame advantage to lead 9-7 in a high-quality morning session.
|Mark Allen facts|
|Born:22 February 1986 (Age 29)||Turned professional: 2003|
|Nickname: 'The Pistol'||Current ranking: 12 (Highest ranking 6)|
|Home: Antrim, Northern Ireland||Ranking event wins: 2 (World Open twice)|
|Highest break: 146||World Championship best: Semi-final 2009|
Breaks of 81 and 109 kept Allen on top with a 11-9 lead at the mid-session break.
But Hawkins began to get on top in the tactical battle.
A crucial 21st frame went the way of Hawkins thanks mainly to a carefully-judged snooker and he started to take his chances with ruthless efficiency.
Allen added: "I should have gone 10-6 up and that would have been a pretty commanding lead.
"And I also had a good chance to go 12-8 up as well and these are the things that can cost you.
"As the match went on Barry got stronger and I got weaker so credit to Barry."
Hawkins will play Neil Robertson in the quarter-finals.