Why I Snuck Into My Kid's Room and Read Their Diary Last Night

Last night, I couldn't sleep. As someone in their 40s, you'd think the worst of my insomnia would be over by now, but nope. Worrying about bills, health issues, the future... it all piles up in your mind until you can hardly breathe. I got out of bed and decided to make some tea, as usual. But on a whim, I walked past my son's room. He’s 16, and he has this small diary that looks old-fashioned compared to his other electronics. It just sat there under his pillow, unguarded. My curiosity was too much for me. I picked it up and started reading, hoping for something to distract from my worries. The first few entries were normal teenage stuff, how he likes girls, how school is tough, things like that. Then I got into a section where he was really upset about his friend’s parents splitting up. His best friend had been in tears about it for weeks. But then the last entry, written just yesterday, made my heart sink. He mentioned feeling overwhelmed and alone at home. He said there were too many fights between me and his dad lately. It wasn't anything specific or new to him, but reading that hurt more than I expected. I felt this urge to tell him it was going to be okay, but then I thought about how my own issues are probably contributing to the problem. Now here I am, thinking what a terrible parent I've been for invading his privacy like this. Part of me wants to face him and apologize right away, but another part is worried about making things worse if he finds out I read it. So here's my question: Is reading your kid’s diary ever justifiable? Am I being overprotective or should I have left that private space alone? What would you do in this situation? Your thoughts are appreciated.