It cost the 26-year-old from Newcastle-under-Lyme a quarter-final against the game's biggest draw, Ronnie O'Sullivan.
"I can't be too hard on myself. I hope there'll be many more possibilities in the future," he told BBC Radio Stoke.
"It was good to go deep into a tournament and feel involved. I've not done that too many times."
The only other time Highfield had done so since turning professional in 2010 was at the Paul Hunter Classic in Germany in August.
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He also came through three matches there to make the last 16, but his progress at the York Barbican was a much bigger deal, as it came in one of snooker's "Triple Crown" of events.
Two 6-5 wins, followed by a 6-2 third-round success against Peter Lines, earned Highfield a best-ever pay cheque of £15,000.
Although he would have banked £22,500 for beating 1999 and 2003 world champion Williams, Highfield's efforts on his 26th birthday have given him a taste for more.
"The way I played against Lines, I can take a lot of confidence from that," he said.
"I've got used to playing small arenas, but it's about getting used to being out there in front of a massive crowd. Hopefully I can do that as much as I can."
Liam Highfield made for a frustrated figure at the UK Championship in York after his final-frame defeat by twice former world champion Mark Williams.