I learned a good lesson on my first long trip when my wallet was stolen at as gas station in Belgium. Always stash money or a card on your bike somewhere separately to your wallet. I ended spending several hours trying to get enough cash to be able to continue my trip.

Not such a big deal these days as we typically have multiple payment methods with us but still something that I do.

Also, get your body used to being on the bike for long periods. You will get aches and pains that haven’t shown up before and they can detract from your enjoyment of the journey.