The Dutch middle-distance runner also admits to a feeling many of the 45,000 amateur runners tackling the London Marathon will sympathise with: nerves.
"My feeling is nervous, and curious at the same time," Hassan told Reuters in an interview.
"Can I defeat the marathon, or is it going to defeat me?"
After gruelling training runs without food or water during the holy fasting month of Ramadan, Hassan said she has no particular time in mind for finishing the race.
At the Tokyo Olympics in 2021 Hassan dominated the track with a rare triple, winning gold in the 5,000 metres and 10,000 metres as well as bronze in the 1,500 metres.
If Sunday goes well, she may consider another marathon in the autumn, she said, adding however that she still loved track and didn't yet know how her 2024 Paris Olympics plans might change.
In what race organisers say is the greatest ever elite women's field at the London Marathon, Hassan is up against defending champion Yalemzerf Yehualaw, world record holder Brigid Kosgei, and Olympic champion Peres Jepchirchir.
Organisers say they see the world record of 2:14:04, set by Kosgei in Chicago in 2019, being broken on Sunday.
"In terms of who's going to win, I do not have a clue," race director Hugh Brasher said. "If that comes down to a sprint finish... I think it's going to be fascinating."
Britain's Eilish McColgan, also set to run her debut marathon, said late on Thursday she is getting treatment for a knee issue and waiting to see how it responds before deciding whether to race.
