The Belgian made his return to racing at the GP d'Isbergues, two months after the brutal Tour de France crash and took the win.
"I am already back after two months and I took my first victory of the season," he said.
"My goal was to get a win in this last part of the season. I know it was a bit crazy and 99% of the riders would probably just be happy to come back, but I really believed I could do it."
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Gilbert hoped to return before October 7 at Paris-Tours, which he won in 2008 and 2009, but his comeback happened even earlier.
Philippe Gilbert has been out of racing since the Tour de France Photo : Yuzuru SUNADA
(Image credit: Yuzuru Sunada)
"I've worked so hard to get back here today. Honestly, there have been some difficult moments when I have been at home fighting to make this comeback," Gilbert continued.
"I have had a great team around me at home but you still have to do the work yourself, to put in the energy and focus.
"After my crash, some of the most positive opinions I heard were that I should be happy if I were back on the bike within four months."
The 36-year-old Belgian admitted that "maybe" the crash could have closed his career.
Gilbert that day climbed from the ravine and amazingly finished the stage with blood running down his left leg.
He earned the most combative rider award for the stage, but scans revealed a broken kneecap and ended his race.
Sunday's race in northern France was shortened due to heavy rain. Gilbert attacked to form a large escape group and again at 20 kilometres to free himself of that move with Christophe Laporte (Cofidis).
Team-mate Florian Senechal attacked from behind and allowed Gilbert to sit on his rival's wheel.
"In the last kilometres, seeing that Florian was coming from behind, I could save a bit of energy," he added. "In the final, I just felt I couldn't lose."
Gilbert was second in E3 Harelbeke behind team-mate Niki Terpstra and third in the Tour of Flanders, again behind winner Terpstra, but he had yet to win in 2018. The victory also added to Quick-Step's tally of 69 season wins.
"I am just really happy that I got to taste the victory too in what has been a fantastic year for the team," Gilbert said.
"Now I am looking forward to what the rest of the season can bring me. Nothing is impossible on this team, and you could see that today."
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