You will get lonely

This is especially true if you come out for a program and not know anyone. Of course, you will make friends but for the first couple of days or even the first week while you're introducing yourself to people and trying to find your crowd you'll experience loneliness and it can bum you out. The loneliness will quickly make you homesick and you'll wish that you never decided to go abroad in the first place.

You'll realize you both underpacked AND overpacked

I felt like I underpacked because I miraculously fit everything in one suitcase, but once I got everything out, I also realized I overpacked. I wish I knew that London is at its coldest post-Christmas and that it would still be warm in September. It didn't take long for me to notice I over-packed coats (my southern California self-was so eager to finally put them to use) and also packed almost every sweater I own. It's definitely a challenge to stay cool when your clothing options consist of turtlenecks and wool sweaters. Lesson learned.

You'll overspend

Even if you try really hard not to, you will overspend. You can budget ALL you want, but in your first couple of weeks, money will go so quickly. You'll be buying essential things you need but didn't pack, things to decorate your room and other random things you totally forgot you'd need. Let's not forget that no matter how hard you try, there will be a night or two where you just spend way too much. Don't be so hard on yourself and just budget for future weeks.

You'll get lost

I'm talking about constantly walking the wrong way, getting on the bus going the opposite way, or having your bus stop in the middle of its journey because the roads are shut down for a protest and you now have to walk the remaining 1.5 miles to your destination. Nobody likes to admit they get lost but seriously, you will get lost, pretty much every day.

You'll have a ton of blisters

Once you move abroad, especially to Europe, you're going to be doing a lot more walking than you're used to. For real, I average about 20,000 steps now since I don't drive anymore. What you don't anticipate is the number of blisters you'll have. Sure those shoes were comfortable back home, but they're not going to be with the amount of walking you'll do. Get some shoe insoles and wear comfortable shoes if you know it's going to be a day you're particularly walking a ton or need to run errands.

You'll buy necessities and then realize you bought the wrong thing

This will mainly happen when you're in a rush and realize that you suddenly need shampoo and conditioner, only to find out that instead of buying one of each, you bought two bottles of shampoo. You'll be super frustrated because you probably won't realize until you're in the shower wondering why you can't find the bottle that says conditioner.

So much jet lag

I've never been jet-lagged more than a day or two, until I moved abroad. I was jet-lagged for at least a week and no matter what I did (force myself to bed at London time) or wake up early, I was constantly on California time and it drains the life out of you.

You have to figure out a whole new area 

You knew exactly which places back home to avoid and you knew exactly which way, if not multiple ways, to get home. Now you're in a whole new country where you're not exactly sure just how safe it is at night, or down certain streets. Be cautious and be patient, you will figure it out and it will come with time.

You'll accidentally stay out too late and panic about getting home

Not all public transportation runs 24 hours every day, and you're probably too tired at this point in the night to figure out which night bus(es) to take home. Yeah your Uber might be surge-charging right now, but you know it's your best/safest option and you'll just plan ahead next time.

You have to learn a whole new schedule

Sure your CityMapper App tells you the commute times for all these different routes, but you need to go a step further. You don't realize that if you're commuting during rush hour, there might not be space for you on the first train that comes by. Maybe even the second. Even though the tubes come through frequently, those few minutes between each train can add up and soon you'll find yourself running late to everything. You might have to adjust the time you eat or run errands because some places close way earlier than you're used to back home.