How did you know your marriage was over?

Feels like my marriage is falling to pieces more and more with each argument. We try our best to keep it going try everything to please each other but it's always something. There's never true happiness. If there is I'm the only one who is experiencing it. He's never happy with anything. Nothing is ever good enough. I feel so drained and lost. I love him as a person I've loved him for 8 years. It's different now though. Idk how did you know it was over?