Start with a city that speaks your language. Stay in one place for at least 3 nights before moving on. Talk to bartenders and baristas. Eat at the bar. It gets easier faster than you think.
First trip abroad: spreadsheet, hour-by-hour itinerary. Now: a flight in, a flight out, maybe one reservation, and the rest is on the day. It's scary and also the most fun way to travel.
Multi-currency accounts with real exchange rates and no foreign transaction fees. I've saved hundreds on a single trip. Stop paying your bank's 3% vacation tax.
Mine: a random Tuesday in Lisbon, got lost in Alfama, ate pastel de nata on a tiled stoop, watched the sun set over the Tejo with strangers who turned into friends. No plans. Best day ever.
One carry-on. Three weeks. Everything fits and stays organized. I held out for years thinking it was hype. It was not hype.
Everyone goes to Paris, Rome, Tokyo. Try Lyon, Bologna, Osaka. Cheaper, less crowded, and you'll eat better. What's your favorite 'second city'?
I've met Europeans who've done more of the US parks than most Americans I know. Start with the big five in Utah. Book your permits early.
Spent a week at a resort in Mexico and left feeling like I'd been to a theme park version of a country. The real places are just outside the gates. Go outside the gates.
Went in mid-November, stayed a week, saw Fushimi Inari at sunrise with maybe 20 other people. The shoulder months are the secret to temples, ramen shops, and everything else.
Hiked the Tour du Mont Blanc — 10 days, three countries, sleeping in mountain huts. Nothing I've done since has come close. What was your 'ruined the rest' trip?