"Life has to go on, we can't live in fear," Londoner Marcus Schuster told ABC News.
"Life goes on in this city. You can see it," he said. "What they try to instill is the fear to, you know, like going out in the streets. But that's not going to happen in London, that's not happening in Manchester."
Seven people were killed and dozens injured after the attack Saturday night that began with a van plowing into crowds of people on London Bridge and continued at nearby Borough Market when three knife-wielding men jumped out of the vehicle and began stabbing people. Three suspects were shot dead by police.
The attack came less than two weeks after a suicide bombing at an Ariana Grande concert in Manchester that killed 22, and several months after an attack on London's Westminster Bridge that killed five.
We are all shocked and angry today - but this is our city. We will never let these cowards win and we will never be cowed by terrorism. pic.twitter.com/kcosumkdCR
In the 1940s London proudly proclaimed that "We Can Take It." They still can. pic.twitter.com/JFy1fz0mzW
The saying "London Can Take It" became popular after a short propaganda film was widely distributed in 1940 throughout the U.S. The film "conveys the spirit and atmosphere of the 1940 blitz on the capital" and is "historically one of the most important war films," according to The National Archives.
The motivational saying "Keep Calm and Carry On" also stemmed in the World War II era in England. Posters were produced in 1939 in preparation for the war, according to the website that features officially licensed merchandise with the saying.
The Saturday night attack came days before a U.K. general election on Thursday.
Campaigning was called off until Monday in light of the attack, but Prime Minister Theresa May said the election will take place as planned, expressing the country's resolve.
"Violence can never be allowed to disrupt the democratic process," she said. "So those campaigns will resume in full tomorrow, and the general election will go ahead as planned on Thursday."
A moment of silence will be held Tuesday at 11 a.m. local time "in remembrance of those who lost their lives and all others affected by the attacks in London Saturday night," according to an announcement from the national government. Flags will remain at half-mast on Whitehall government buildings until Tuesday evening.
ABC News' Janet Weinstein contributed to this report.