A lot of the support Mr Langman received was from the charity, which still helps him now.
"If I never had their help, things wouldn't have come out so good," Mr Langman said.
"I probably wouldn't have my job, or the focus I do now."
Mr Langman works part-time as a motorcycle mechanic. The three to four hours he works a day feels like eight hours and he gets tired easily.
Mr Langman's injury affected every aspect of his life and the journey of rehabilitation was a constant struggle, he said.
Another effect from his injury made him more prone to bad mood swings, sometimes getting angry over things that did not bother him before.
"I need people's help. As much as I don't like it, I like to do things on my own, I need it."
Mr Langman said he enjoyed the day yesterday and rode some laps of a gymkhana that was on offer.
"I'm here to show my appreciation to all those people who help people with brain injuries."
Headway liaison Dianne Beveridge said: "Today is a real privilege being asked to be part of this because the public don't necessarily equate a brain injury or head injury with long-term rehabilitation."
Mrs Beveridge said when someone broke an arm, there was a set timetable of recovery before the patient was back to normal.
"But the people I see, many of them had their accident five, 10, 15 even 20 years ago."
Organiser Damian Fleming, who owns Bayride Motorcycles, said the event was sparked by Mr Langman's situation.
"It's a charity event for Sean," Mr Fleming said.
"People pay their $20 and we give that to charity."
Mr Fleming said he had hoped for a few hundred people to turn up but was still pleased to be able to help the cause.
"We've had families turn up, including a 5-year-old, an 8-year-old and parents come all the way from Whangarei especially. That's pretty cool," Mr Fleming said.