Expectations are the road to hell. Too often we get so attached to how we think things "should" be that we are unable to be with what is.
First, identify all the "shoulds" you have about your daughter. Examples: "She should have stayed with ....", "She shouldn't rush into another relationship."
Next, let go of the shoulds. You might even want to write them on some helium balloons and literally let them go. Or write them on a piece of paper and shred it.
Then, write down what is.
Then, allow yourself to feel all the feelings you feel about what is. Really let them flow. If you need to cry, then cry. If you need to sit in the car and scream, then scream.
Now you can choose how to respond to what is rather than being stuck in reaction to it not being how you want it to be.
She is a grown woman. Yes, she is still growing and learning and may make some choices that have some "negative" results. Yep. That is life. We are all there and yet we all seem to manage to get through the times of struggle. Give your daughter the gift of respect. Allow her to be 100% responsible for her choices. Be her mom, but from a place of support rather than fix it. The reality, as you well know, is that we can never fix or fully protect our children just as noone can do it for us.
We are all here for our own journeys. We all have the capability within us to make choices, deal with consequences, and to make new choices. Allow your daughter the right to learn how to do this in a way that works for her rather than expecting her to do it in a way that works for you.