Almost every trip teaches me something about myself, the world and what not to do next time. Here are three hard-won travel lessons that may help you learn from my mistakes.

Whenever possible, I book nonstop flights. Nonstops may cost a bit more, but they avoid the inconvenience of layovers and the stress of possibly missing a connection.

Sometimes, of course, nonstop flights aren’t available or affordable. What you don’t want to do, I learned through bitter experience, is try to save money by booking flight legs with different, unaffiliated airlines - especially if you’re dealing with luggage or customs.

In 2017, my husband, daughter and I flew to London and then Barcelona, Spain. That part went fine; it was coming back that became a nightmare. The Barcelona-to-London flight was delayed. When we landed at Heathrow Airport in London, we learned we had to pick up our luggage at baggage claim, go through customs , check our bags at another airline’s ticket counter in a different terminal , get through security and sprint to the gate to make our connection - all in about an hour.

Somehow, incredibly, we made our flight home, but my heart didn’t stop pounding until we were well over the Atlantic Ocean. Now I make sure to book through a single airline and its partners. Our luggage is checked through to our final destination, and flight delays become the airline’s problem to fix.

For years I blithely traipsed around the world, not thinking about what might happen if I got sick or injured far from home. Then my father suffered a stroke while visiting his sister in Florida. The medical evacuation flight to get him back to his home in Washington state, with the required attendant and other necessary medical care, would have cost over $100,000.

Sadly, he never recovered enough to make such a flight. But I realized how vulnerable I’d been, especially traveling in places with poor medical care. Now I make sure that whenever we’re away from home, we have travel insurance that includes medical evacuation. If we’re traveling outside the U.S., I ensure we have health insurance coverage as well.

These days, travelers also have to worry about COVID-19. Although the U.S. has dropped its requirement that incoming travelers produce a negative COVID-19 test , the Centers for Disease Control and Prevention advises against traveling if you have symptoms or test positive. That could mean a week or two of unexpected hotel and meal costs, so I make sure our travel insurance covers COVID-related expenses and that the “travel delay ” portion has a high limit - such as $250 per person per day.

Other things can go wrong on a trip: flight delays and cancellations, lost baggage, accidents in rental cars. I charge all of our travel on credit cards that provide coverage for such minor disasters. I particularly like the kind of rental car coverage that’s primary , meaning that your auto insurer never needs to know you caused an accident or damaged the rental car. Many cards offer secondary coverage , which typically means your insurer has to be notified and the card pays only what your insurance doesn’t, according to the Insurance Information Institute.

This is a lesson I didn’t have to learn the hard way: The one time a rental car agency tried to bill me for a door ding, I notified my credit card company. I have no idea if the claim was paid or dropped; I just know that I didn’t have to deal with it after that.

Many credit cards offer general travel rewards that you can transfer to the issuer’s airline and hotel partners. But some credit card companies also offer their own travel portals. These function a lot like online travel agencies such as Expedia and Orbitz, allowing you to search among various travel providers and then book using your points.

I don’t typically use online travel agencies, because I think I get better customer service by booking directly. But earlier this year I decided to give the travel portal option a whirl - and lived to regret it.

The flight I booked from Los Angeles to Vienna with my credit card points had a stopover in Istanbul. A few weeks after booking, I got an email that the leg from Istanbul to Vienna was canceled.

I logged on to the airline’s site, expecting to be offered options to rebook the canceled leg. Instead, I got a message that my itinerary could not be modified. When I called the airline, a customer service agent told me I needed to call the credit card company. When I called the credit card company, I was told I needed to talk to the airline.

I tried emailing to get the issue resolved, with the same result. Finally, in desperation, I reached out on Twitter. It took a few more rounds of finger-pointing, but eventually I was able to cancel the booking, get my points back - and swear off ever using a travel portal again.

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This column was provided to The Associated Press by the personal finance website NerdWallet. Liz Weston is a columnist at NerdWallet, a certified financial planner and the author of “Your Credit Score.” Email: lwestonnerdwallet.com. Twitter: lizweston.