Williams, who spent time on-loan with Ipswich Town, was arrested for dangerous driving in August 2023, before he was eventually released by United last summer and took a complete break from football.
He signed with the Tigers a fortnight ago and feels ready to relaunch his footballing career.
"It was in the moment I was in, I wasn't in a good place," the 24-year-old told BBC Radio Humberside.
"It's a big regret and I've learned from my mistakes. I was still a young boy and I'm grown up now. My focus is back on football and that's all I want to do now.
"I just fell out of love with football. Things were going on off the pitch, I had a lot going on and I just couldn't focus on my football.
"It just got to the stage where it was too much for me to carry on and it was better for me to take a step away and a step back and try and find myself again."
Williams added, "I was working in silence. Everyone was questioning what I was doing but I was working the whole time.
"I was keeping fit and making sure I was ready to step back into football. It was always the aim.
"Just before pre-season I felt ready to step back into football and it was important that I did get the training and friendlies in.
"Now it's just building and building, I'm still not 100% but I'm sure in the next weeks and months I'll be there."