De Guzman earned a standing ovation after bending in a stunning set-piece to cap Swansea's 3-0 Europa League win at Valencia on Thursday.
Dutchman De Guzman said: "It was probably in the top three of free-kicks in my career.
"You don't score many goals like that, especially playing in a stadium like the Mestalla.
"It was a goal that was really special for me.
"I practise it quite often - and I have been doing it ever since I was young.
"It is one of my weapons, you could say. I have been taking set-pieces since I was a kid. In the academy at Feyenoord we practised it a lot.
"They groomed me there to take free-kicks and I took it with me."