Swiatek crouched down on the clay and shed tears at the end of a fierce battle with unseeded Czech Karolina Muchova (26) in which she dropped her first set in two weeks in Paris before sealing a 6-2 5-7 6-4 victory.
The world number one said she was left almost surprised that she closed out the victory as Muchova - who beat second seed Aryna Sabalenka (25) with a late fightback in the semi-finals - double faulted on match point to bow out.
"I saw all these matches of Karolina when she was actually coming back from scores like that before match point, I wasn't really thinking it's going to happen now. I just played and I just gave it all," Swiatek told reporters.
"It's hard to describe. There was a lot of happiness. I felt suddenly tired of these three weeks. Maybe my matches weren't physically exhausting, but it's hard to keep your focus.
"And the whole swing. Since Stuttgart I haven't been home. So I'm happy I finished the whole claycourt swing so well, and that I survived. I'm never going to doubt my strength again maybe because of that."
Swiatek said she had no regrets about dropping the second set after going 3-0 up.
"I just looked forward and I said to myself, 'OK, you know what? I'm going to give it all.' I wasn't thinking or analysing. I played my game, used my intuition, and that really helped," she said.
"After so many ups and downs, I stopped thinking about the score. I wanted to use my intuition more, I knew that I can play a little bit better if I'm going to get a little bit more loosened up. It helped, for sure, in the third set."
