Trista and Ryan Sutter mark 17th anniversary amid his struggle with mystery illness

It's been 17 years since Trista and Ryan Sutter got married, and as he continues struggling with a mystery illness, the couple are expressing their gratitude for each other.

The Sutters, who met on the first season of "The Bachelorette," took to social media Sunday to wish each other a happy anniversary with sweet messages on both of their Instagram accounts.

Trista, 48, posted a photo of her husband from their wedding day and shared why he's "more handsome today than he was on this day 17 years ago."

"Because he continually works to better himself...and us. Because he is the most humble, hard-working, generous, sincere, kind-hearted human with the biggest heart and even bigger muscles," she wrote.

Trista also called out her husband's "bravery and resilience," qualities especially important as he continues to be affected by a sickness that's still undiagnosed. She revealed last month that he has been "struggling for months" with the illness.

"This guy...my rock, my best friend, my hero, my love...is struggling. Not everyday, and not to the point that he can’t work or cook or exercise or be with family, but enough," she wrote in a Nov. 28 post.

"We lived a fairy tale on TV and have a great life for all intents and purposes, but answers would be nice. So, I’m going to keep praying for answers and am hopeful that if you are the praying type, that you’ll think of Ryan when the time comes to send up a message."

Ryan, 46, is grateful for his wife's support, thanking her in his anniversary tribute posted Sunday for always being there for him.

"Through good times and bad, sickness and health, blue skies and rain," he wrote. "You’ve stood by me through difficult times, supported me through change and sympathized with me through struggle. You’ve shown me grace and taught me gratitude. You challenge me and inspire me.

"You are my light, my reason and my hero. You are the best thing that’s ever happened to me and the love of my life."

After Trista revealed Ryan's health struggles, he explained in his own series of separate posts that he initially felt ill when he was training to resume his firefighter career earlier this year.

"Towards the end of that process I felt more and more worn out and began feeling occasional 'flu like' symptoms," he wrote Dec. 1. "I was tested for COVID multiple times but never tested positive. I completed the academy and believed/hoped I would begin to recover and feel better. It’s been five months now and, if anything, I feel worse."

He went on to describe his symptoms, which include fatigue, muscle aches, fevers, headaches, congestion and full body itching.