Mr Bryan began his journey at the Napier school as deputy principal but moved into his first principalship one term when the position was vacated.
"It's been a steep learning curve. I worked things out and had a new deputy principal start with me. Together we made the rules up as we went along, had a lot of fun and ticked a lot of boxes. I think the school has changed and is hopefully a better place than it was 12 years ago."
The 62-year-old was the first male principal at the Catholic school, and will go on to be the first at his new school, St Catherine's College in Wellington, as well.
"I've never, ever felt uncomfortable in the role. I've just been who I am and it's been about highlighting your passion for learning and making a difference in the lives of young people, getting to know your community and working alongside them."
With four grown children in Wellington, he and his wife Julie, formerly an English teacher at Napier Girls' High School, made the decision to return to the capital after recently becoming grandparents.
Throughout his time at Sacred Heart he's overseen significant changes in the school including the demolition of the hostel, opening of the new mission centre and the 150th Jubilee celebrations this year.
Speaking from his office on Bluff Hill, Mr Bryan recalled a former colleague asking him in jest what he knew about being a principal before he made the move to Hawke's Bay.
"They were right. It's a leap and a first-time principal is just that. You've not been a principal before and the role is very different to other members of a leadership team.
"The buck stops with you and the number of areas of compliance are mind boggling. You tend to become competent at lots of things in a smaller school too."
His biggest challenge? The ambivalence of the Catholic community in Hawke's Bay.
"They dine out on Catholic primary education and then they jump because they perceive, as I said in my prize giving speech, juicier options elsewhere and they go to state schools.
"It's that perception versus reality thing. Our academic achievement is outstanding but getting that across to people is hard work because they see us as a small school that has limited opportunities when in reality our graduates are achieving just the same as the students from any school."
He said he was confident the young women at Sacred Heart College were provided with every opportunity to flourish and would greatly miss the school community he had become so enmeshed in.
"I'm going to treasure my 12 years here, it has been very special. We arrived in Hawke's Bay knowing one family and now, through the tentacles of the Hawke's Bay school community, we know literally hundreds of families.
"You invest a lot of emotion and energy into the leadership of a school and there are massive returns with that and so you say goodbye to all of that and start again."
He will be succeeded by former Havelock North High School deputy principal Maria Neville-Foster.