I'm an American who visited Iceland for the first time. Here are 7 mistakes I made.

Iceland has been at the top of my travel bucket list for years, and I thought the country's gorgeous scenery and famous tourist attractions like the Blue Lagoon lived up to the hype. However, I made a few mistakes along the way, and would do some things differently if I ever make it back there again.

I didn't check a bag for my five-day trip to Iceland, but I ended up having to gate-check my carry-on luggage because it was too large according to Icelandair's baggage-allowance rules. 

While I've taken the same suitcase aboard many flights without issue, Icelandair only allows carry-on bags no larger than 21.6 inches tall, 15.7 inches wide, and 7.8 inches deep.

Thankfully, my carry-on made it to Iceland and I wasn't charged any extra fees. Still, if I flew Icelandair again, I'd bring a smaller suitcase.

When I landed in Iceland, I expected to pick up my rental car at the airport, but only four companies were actually located onsite in the arrivals terminal: Avis, Budget, Europcar, and Hertz.

The rental company I used, Economy Rent A Car, was located about a 10-minute ride away via a shuttle that only came every 30 minutes, which could be one reason why it was cheaper than its competitors. 

I paid $348.66 for five days, but next time, I'd pay a little extra for the convenience of getting out of the airport faster.

Since I was going to be swimming and taking pictures in several lagoons, I wanted to be extra careful and protect my phone with a waterproof case.

However, I found that the case actually made my phone bulkier and more difficult to use. The case also obscured my photos. I ended up taking the case off and just holding my phone very tightly while in the water, and noticed lots of other people doing the same.

Even though it only cost $6.99, I regretted buying what turned out to be an unnecessary item.

The weather in Iceland can be unpredictable, even in late spring and summer, so I packed lots of layers and brought my warm winter gear in case I needed it.

I got extremely lucky with the weather I experienced during my trip. It barely rained, and I even had some perfectly sunny days.

While I was glad to have brought my waterproof winter coat, I barely wore my hat, scarf, or gloves. The bulky items took up valuable space in my suitcase, so I wish I'd left them at home.

I visited three lagoons during my trip to Iceland: the Blue Lagoon, Sky Lagoon, and Secret Lagoon.

The Blue Lagoon's cheapest admission was $93 and included a locker, a towel, a mineral face mask, and a drink from the bar inside the lagoon. The Sky Lagoon's cheapest ticket cost 7,990 ISK, or about $60.43, and included a locker and a towel. The Secret Lagoon cost 3,300 ISK, or $24.96, and only included a locker.

At the Blue Lagoon and Sky Lagoon, towels were included in the cost of my ticket. I'd assumed that the Secret Lagoon admission would include towels as well, but that wasn't the case.

I made the mistake of swimming in the steaming geothermal pool before realizing it cost 500 ISK, or about $3.78, to rent a towel. I had to dig around for my credit card while dripping wet in 60-degree weather.

I was initially confused when I saw signs in grocery stores with prices like 1.999 ISK per kilogram. I thought I was getting an amazing deal until I realized that it actually meant 1,999 ISK.

It turns out it's not unique to Iceland — many other countries in Europe and around the world use decimal points to separate thousands, according to Cornell University's Office of the Treasurer.

I visited Iceland in June, when the sun never fully sets. Because the Earth's Northern Hemisphere tilts towards the sun during the summer months, countries north of the Arctic Circle like Iceland, Sweden, Finland, and Norway are continuously exposed to sunlight, resulting in a phenomenon known as the "midnight sun."

Iceland's constant daylight tricked my body into thinking it wasn't as late as it actually was. Darkness usually cues the body to produce melatonin, the hormone that helps our bodies get ready for sleep. Without a sunset or a dark night sky, I found myself accidentally staying up later than I normally would simply because I didn't feel tired at my usual bedtime.

While I did appreciate how the midnight sun helped me navigate more easily and made me feel safer walking around alone at night, the lack of sleep left me feeling exhausted throughout my trip. Next time, I would pack some over-the-counter melatonin supplements to help normalize my sleep schedule.