What if it goes wrong? Then you'll look at your options and choose what to do accordingly.
Decide in advance what is critical. And then plan on such a way that you can make that happen. All the rest is bonus.
I'm writing this from my hotel bed instead of my own house, because somehow my train got delayed so much we could not get home. There was no stress, I even packed an extra set of clothes for this trip in case something went wrong.
We had some other options, like renting a car and driving home or sleeping in a different city. This was the most relaxed option. I just asked my housemate to receive a package tomorrow, moved some things around on my calendar and chose to be here.
And for the rest it's practice. Acknowledge yourself for the situations that you handle calmly and when you were in a stressful situation, write down what you can do differently.
A lesson I wrote down for today is to subscribe to a texting service whenever I make long travels. That way I can act even sooner next time something happens.
Just breathe and trust yourself. You got this 😉