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British and Commonwealth super-welterweight champion Williams, 24, trained alongside Blackwell under trainer Gary Lockett.
"It was very upsetting. I was supposed to fight the week after it happened, which obviously didn't go on," he said.
"You look at things differently and you're a bit wiser in your approach."
Williams will fight mandatory challenger Ahmet Patterson in Cardiff in a rearranged headline bout on 26 November.
"I'm a little bit more sensible" Williams added.
"I try to avoid sparing too often and taking silly shots and getting into tear-ups in the gym, I don't think it's wise. It makes me a little more wary."
Super-welterweight Patterson goes into the contest undefeated on a run of 17 wins under his belt and Williams says he will be a formidable opponent.
"He's tough to prepare for if you're at that quality and you are a good fighter, as I believe I am. I'm just going to get in there and adapt," Williams said.
"A world title fight is a tremendous motivation. Obviously I've got to get past Ahmet first and he's quality, he's skilful.
"There's no certainty that I'm going to come past that but I believe that I will. There are massive things to come in the New Year."
Welsh boxer Liam Williams says he is "more sensible" since gym-mate Nick Blackwell fell into a nine-day coma after a British title fight in March.