Gribbin, now of FC United, has now gone four years since he moved on from United and is now 25 years old.
Once described as the English Messi when he was a teenager, he has failed to live up to his potential.
Speaking to The Athletic, he said: "I have to take some responsibility and say, when I was younger, I didn’t handle myself in the best way. I let myself down massively at times.
"Towards the end of my time at United, I was difficult. I wasn’t getting a chance in the first team and I was unhappy about it. I went into self-destruct and started getting up to the wrong things away from football.
"I was immature and, because I was so talented, I think I relied on it. I abused it over the years. I relied on my talent getting me through all the time."