1. It is very clear you are no longer "new"
Once new batches of teachers start to come in to town, in awe of everything around them, almost in a "Korea daze"; it is then you realize how far you've come. Sometimes you forget what made this place so magical in the first place. Newcomers are a friendly reminder of this,
2. All things get increasingly easier
Buying bus tickets on a Korean app, chatting with taxi drivers, ordering from a coffee shop, going to the doctor. They all get easier. And it starts to make Korea feel even more like home.
3. You say too many goodbyes
If you've stayed a second year in Korea, chances are you like it (somewhat, I would hope) and have made a decent amount of friends. Especially if you've stayed in the same city. However, many do decide to leave after their one year contract is over, and this usually calls for some goodbye celebration/mourning. Not only does the quantity of goodbyes increase dramatically, but the quality of the emotions attached to these people also increases, making goodbyes significantly more difficult.
4. The thought of a 3rd year sounds either really repelling.....
There are always going to be little struggles living in a different culture than your own. After living in a foreign country for almost two years, things that used to bug you a little bit are magnified. (Or in some cases, maybe you have completely adapted to them). There are just some days where the spitting, stares, and crazy driving get to you, and leaving seems like the clearest option for your sanity.
5. ........or really tempting
After almost two years you also realize how much this country has to offer. On all fronts. Outdoor activities, festivals, food, people, learning, etc. You could go somewhere every weekend and still not run out of things to do, and it's not a big country! You also start to realize how lucky you are to be here. Relatively stress free, no rent, an apartment to myself, a great social life. When you start thinking about leaving and the realities that come with it (e.g., paying rent like a normal person), this makes you appreciate the present even more.