"It's okay to be not okay - and it's definitely not weak to speak."
The annual Mental Health Awareness Week, which kicks off today, aims to get people talking about the issue more freely and equip people with skills to help deal with it.
"It took me a long time and a lot of speaking out and speaking up to get help but I got there eventually, to the point I'm starting to really enjoy life," Shewry said.
His mental illness started when his wife Janna was pregnant with their first child - Emma, now 4.
The pregnancy was stressful, Janna's waters broke at just 20 weeks and they almost lost the baby. His job was tough too.
"I didn't know it at the time but in hindsight that's when everything started," he said.
"Fast-forward probably a year since our daughter was born, I went through a really difficult period emotionally, just a lot of little things - a small addiction had developed with some gambling, I was really out of sync with life.
"I struggled to get out of bed in the morning, I struggled to socialise, I hated going out.
"Probably about a year later, I was breaking down in front of my wife and she thought I might have been depressed."
An online test indicated Shewry likely had moderate level depression. A few days later he gathered the courage to see his doctor.
Prescribed antidepressants, it took Shewry almost a week to start taking them.
"I was thinking I didn't want to be on pills my whole life - just the whole stigma around taking pills, and I was incorrectly thinking they were crazy pills and I didn't want to take them to be happy," he explained.
"But I did take them and things levelled out for a few months.
"I was still managing work and life. But I wasn't enjoying the things I used to enjoy, for example golf - just the thought of going outside and playing ... I had no enjoyment.
"Life wasn't being lived how it should have been."
About two years later Shewry stopped taking his medication.
By then he and Janna had welcomed their son Logan, now 2.
He struggled without the meds and started to take them again. Then he began to spiral.
"Life caught up with me," he said.
"All the stresses of a new child, financial stress, a busy time at work, the death of my grandmother ... Everything just snowballed to the point I started fixating on the thought of suicide.
"I got to a point I just hated the thought of living with depression for my whole life."
Shewry knew he was in danger and took seven weeks off work.
"I changed medications and I spent a week trying to get to sleep just in tears because I was scared of what I was going to do to myself," he recalled.
"I would eventually fall asleep with the assistance of sleeping tablets.
"At that point the thoughts and voices were pretty intense, pretty constant. There were some really scary moments."
In the beginning, Shewry didn't speak about what was happening. But when he hit rock bottom he opened up to his wife and close colleagues.
"Whether it's a male thing or a Kiwi thing I'm really not sure, but I downplayed it," he said.
"I was thinking, 'why is this happening to me? I've got a good life, good job, good friends, good marriage, two great kids, healthy kids on paper, everything is looking good'.
"I was trying take the 'harden up' approach, I just needed to get over myself ... and I think that was, looking back now, part of the difficulty, the denial and the misunderstanding especially."
Shewry now accepts his depression is a medical issue and is comfortable asking for help and talking about how he is feeling.
It has taken him more than four years of hard graft to get to that point, which is why he has shared his story - to inspire others to get help.
"Every time I asked for help it was well received but it was still difficult, there's still that stigma that males asking for help is like a no-go," Shewry said.
"I really did bury my head in the sand for a long time ... I knew deep down people weren't going to judge me for it but I still had it in the back of my mind people would think I was just out there to get some sympathy."
He hoped that by speaking up, "ingrained thinking" about depression being a weakness would shift.
"I don't think there's a lot of understanding really, I was experiencing depression and I had no idea what I was experiencing," he said.
"And it's only recently that I fully understand what depression is - it's as much of an emotional and mental thing as it is a physical thing.
"If I had understood a bit earlier I probably would have gotten help a bit earlier."
One in six New Zealand adults would be diagnosed with a common mental disorder at some point in their lives, data from the 2012/13 New Zealand Health Survey showed.
Many of the workshops and tips for this year's campaign were based around the theme, Let nature in, strengthen your wellbeing – Mā te taiao, kia whakapakari tōu oranga, because connecting with nature has been shown to improve moods and promote wellbeing.
Shewry is still working as a detective and recently took a lead role in the investigation and prosecution of Colin Mitchell.
Mitchell was jailed for kidnapping and assaulting a woman at a Riverhead quarry, and also for a historic unsolved rape.
Shewry said his work, often traumatic, hadn't always helped his mental health.
But with good routines - regular exercise, sleep and taking his meds - he is almost back to his old self.
"I'm getting better but there's always room to improve," he said.
"There's going to be some bad days no doubt, but I'm trying to make the most of the good days."
Earlier this year Shewry contacted Voices of Hope - a non-profit organisation that works to break the stigma and provide hope for those struggling with mental health issues by promoting mental wellbeing, empowerment and recovery.
Jackson is a father, husband and New Zealand Police detective who has battled depression and suicidal thoughts. After taking time off work and through the support of his family and The New Zealand Police he was able to fight through his darkest days and now he wants to share his story to help other men know that it’s not weak to speak.
"For me, it got to a pretty real place where I was genuinely wanting to leave this earth for good because it just got so hard and a lot of people potentially would not have known I was in that place.
"The more people that know, the more people who can help you.
"Through my very depressed days it's hard to see where the hope is, where the help is - but just knowing someone's there for you ... they might not have the answers but just knowing that they're there for you, that they care about you, that's one thing that gets me through."
WHERE TO GET HELP NOW
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
IF YOU NEED TO TALK TO SOMEONE ELSE
• DEPRESSION HELPLINE: 0800 111 757 • KIDSLINE: 0800 543 754 (available 24/7) • LIFELINE: 0800 543 354 or 09 5222 999 within Auckland (24/7) • NEED TO TALK? Free call or text 1737 (24/7) • OUTLINE: 0800 688 5463 • SAMARITANS – 0800 726 666 • SUICIDE CRISIS HELPLINE: 0508 828 865 (24/7) • WHATSUP: 0800 942 8787 (1pm to 11pm) • YOUTHLINE: 0800 376 633, free text 234 or email talk@youthline.co.nz
There are lots of places to get support. For others, click here.