"I just got sick of it and was not enjoying it. I was doing stupid things and making bad decisions," he said.
"I was getting frustrated real quick and I know I need to mature a bit more."
Pinn left his employer, New Plymouth trainer Allan Sharrock, after the local meeting and has taken a job working on a dairy farm near Rotorua.
Pinn's decision has left Sharrock stunned and disappointed.
"He just left without saying a word and it took eight days for him to contact me, but at least he's done that now," Sharrock said.
"He has walked away from his employment and I am bitterly disappointed, not only for me but also everyone who has tried to help him. But it's his decision."
Sharrock had developed Pinn into a most promising apprentice giving the young rider a winning double on his first day riding at New Plymouth in May last year, including a successful debut mount on London Express.
Pinn went on to win again on his second day's riding then picked up a treble at Trentham the following weekend and rode 11 winners by the end of last season. He has ridden a total of 32 winners and is fourth equal leading apprentice in the country.
His form resulted in his invitation to compete at the Barfoot & Thompson Jockeys' World Cup meeting and he measured up when successful on Sacred Day.
But all the success and the pressure which goes with it has been too much for Pinn.
"When I got all those winners early on I was put on a pedestal and I just didn't handle the pressure," Pinn said.
"I'd never felt that pressure before. Coming straight from South Auckland I've only had the two jobs and jumped straight into such a professional game."
Pinn began his apprenticeship with Matamata's Te Akau Racing Stables and showed immediate talent, but behavioural issues ended that stint. With the support of National Riding Mentor, former champion jockey Noel Harris, he was given a second chance when sent to Sharrock.
Pinn appreciates the help Harris and others have given him and Harris acknowledges the pressure put on young apprentices. "It's not for the faint-hearted, more so with all the social media today," Harris said.
"With all the expectations it can put 10 years on you. But the pressure is part and parcel of riding. Some handle it and some don't. If they can handle it and do well, they can earn good money and make a good living.
"I always suggest they take a break and reassess everything before making the decision to quit. But at the end of the day it's Wiremu's decision."
History shows some apprentices have quit and made successful comebacks, but for now Pinn, although a natural lightweight and seemingly gifted young rider, is adamant being an apprentice jockey is not for him.
"I want to try something new," he said.
- NZ Racing Desk
