After his win, Allen said: “I was so frustrated yesterday – I’ve been doing things so well on the practice table, being in the gym and eating well.
“After that match yesterday I just went out and had a few drinks and a burger.
“I thought, ‘I can’t play any worse than yesterday’. I was so down on myself, I didn’t want to talk to anyone.
“So I went out, had a few bets and watched the football with my mates. A bit of bad food, slept really well and played much better.”
Allen, who will play 2024 champion Kyren Wilson or 19-year-old Stan Moody in the last 16, said: “Yesterday was absolutely embarrassing, very frustrating and I was completely gutted with my performance.
“I came in today with less expectations, but when you’re out there you realise how much you want it and the fire in your belly comes back.
“I can’t have many more sessions like I did yesterday. I got away with one. It’s not good enough at this level.
“That second session was decent, but I’ve been here for 20 years and I would like to think there’s been better ones.
“I need to be doing that every time I play here. Ronnie [O’Sullivan], [John] Higgins and [Mark] Selby produce that type of session every time.”