The Beaver Falls star originally joined the soap in 2004 as Adam Barlow, the grandson of Ken Barlow.
However, he stated that he "wasn't a very good actor" during his days on the ITV1 drama, which he left in 2007.
"I wasn't a very good actor back then. It's as simple as that," he told the Daily Star.
"I was getting recognised all the time and getting all this attention but I didn't think I had earned it. I knew I was doing a pretty s**t job and I was too scared to learn on the job.
"I was in it for two and a half years and I did definitely improve because I had never acted before in my life. But it was some of the worst Corrie acting, to be fair."
He continued: "I was with two of the show's biggest stars and I had never read a script in my life before. I was a rabbit in the headlights.
"Now I look back and see the amazing opportunity but at the time I just couldn't cope with it."
Robertson added that he would like a comeback on the soap to show that his acting has improved.
"It's not a job you can dip your toes in. It really does take over your life. It's a life choice at the end of the day.
"A part of me wants to go back just for a few episodes just to show I can actually act. Beaver Falls has definitely helped as the response I've been getting from people has been amazing."
Beaver Falls series two starts on Monday (August 6) at 10pm on E4.