My thoughts have been bilingual since I was 12, I think.

I started reading English books when I was seven or eight. Dutch and English are very similar languages so I picked it up relatively fast. English became a subject in what Americans call 4th grade. As you can imagine, I was ahead of the class, and I remained so until graduating high school. I've also had to learn several other languages - at one point I had Latin, Greek, German, French, English and Dutch at the same time. Right now, I'm almost native at English and I can make small conversations in German. The rest was simply too useless to keep up after high school.

I studied abroad in Canada for half a year, which was an interesting experience for the English part of my brain. Up until then, I only had to speak English sporadically to foreigners, but all of the sudden I'm the foreigner. After a week or so I noticed I flipped a switch, so to speak. All my life, whenever someone says something to me, I expect it to be Dutch until proven otherwise. Living abroad and having to get around in a second language changed that. I expected people to answer me in English, and had to put more effort into talking Dutch again. My train of thought was in English and not in Dutch. The weekly Skype call home became more challenging. I didn't expect that to happen so quickly.

The first week back home was really difficult because I tried to talk Dutch using English sentence structures. That was very strange.