A Sad End to What Could Have Been Great

I met Sarah three years ago when we were both new in town. We started off as friends, then things progressed naturally and it felt like everything was perfect. She's in her early twenties and always made me feel cared for, which I really needed after my previous relationship ended badly. Our connection was deep, but it wasn't until a year into dating that we decided to become serious and exclusive. In the beginning, our sex life was amazing. We explored each other thoroughly and felt like there was no limit to what we could try in the bedroom. She's always been adventurous, willing to push boundaries with me, whether it was trying out different positions or toys or even a little CNC roleplay that I initiated (it was all consensual). Those intimate moments were intense and unforgettable. But over time, something changed. I couldn't pinpoint exactly when, but things started to feel routine. We'd still be affectionate, but the spark wasn't there anymore. She would complain about my work schedule being too hectic, and I found myself resenting her need for constant attention. It got to a point where our arguments became more frequent and less about specific issues than an overall dissatisfaction with how we were living. The breaking point came last week when she caught me looking at some adult content online. She was furious because it triggered insecurity, but honestly, I hadn't even thought of her while doing that. It was just a momentary distraction from stress, nothing more. After that, we started talking about whether we were compatible long-term and decided to split up. I feel heartbroken now, though I know the breakup is probably for the best. We've been trying to remain friends but it's hard given how much we used to mean to each other. Writing this out helps me understand that sometimes even good things don't last forever.