Why do i feel like i failed after my breakup?

I'm going through a painful breakup after a 7-year relationship. It was more or less mutual and thankfully we're still on good terms.
What I'm struggling with most is the feeling that I failed the person I loved. For years I wanted to be her safe place her protector the person she could always rely on. I wanted to be strong for her to put her happiness first and to be the kind of partner she deserved.
But during the last 2-3 years of our relationship I wasn't always that person. I became resentful emotionally absent overwhelmed and often not in control of myself. Looking back that realization hurts more than the breakup itself.
The guilt sits heavy with me every day. I keep replaying where I went wrong and wondering if things could have been different.
Has anyone else struggled with this feeling after a breakup? Did the guilt ever get easier to carry? Even a few kind words would mean a lot right now. The pain feels overwhelming some days.