Our phones make our lives so much easier. They have everything, we don't need to carry so many things with us as long as we have them in our pockets.
But when they fail we are in trouble. We are locked out from so many things. We feel handicapped without all that power not available to us.
It's not just all the convenient features like having maps, notes or camera at our disposal all the time. It's not only the possibility to being connected all the time.
I have my train ticket there as well. All my second-factor authentication to all the important systems I would be locked out. My drivers licence. I couldn't even pay for anything without it if I'd choose to leave my cards behind.
It's a wonderful thing having all those things in one device. But it's also scary how much stuff would be impossible without it if you trust everything on it. When you lose it, when it breaks or the battery runs out you are left out. There is nothing you can do.
Of course you can prepare for it. Have your tickets printed as well. Carry all those cards with you all the time. And have backups of your 2fa codes stored somewhere. But that wouldn't be as convenient.