That was the advice coach Alan Storey gave to O'Sullivan when she told him of her eagerness to compete again less than 24 hours after she struck gold over eight kilometres.
"I took his advice but when I woke up this morning I decided to run. I didn't tell Alan until I was jogging to the start line when he rang me on my mobile phone," O'Sullivan said.
"He still tried to dissuade me but I told him if I was a tennis player I would try to win the doubles championships. He gave in, saying: 'Thank God it's not the mixed doubles'."
O'Sullivan's decision brought further jubilation to her army of fans who roared her to victory. After deliberately staying behind the leaders, particularly the local heroine Zohra Ouaziz, who had 25,000 partisan home supporters cheering her on, O'Sullivan gradually moved into contention at the halfway point.
Another blistering finish saw her complete the course in 12 minutes 20 seconds, 14 seconds ahead of the Moroccan with Kutre Dulecha of Ethiopia clinching the bronze medal in a time of 12min 37sec.
Having become the first-ever Irish athlete to win the world title on Saturday, O'Sullivan was advised by her coach and colleagues to rest on her laurels.
"When I crossed the line in yesterday's race I knew I had to go for it," O'Sullivan said. "The longer race was always going to be the tougher but after I finished I decided deep down running again could only be a bonus."
O'Sullivan knew she could expect early pressure from her opponents. "I knew people would go out hard, so I kept telling myself: 'Relax, Relax, don't blow it, they'll come back to you'," she said.