It’s perfectly natural to be scared of change but it is fruitless because change is going to happen whether you want it to or not. Even if you stay here, things are going to change. Remember that and use it to help you get past your fear of change.
You’re also focusing on the negatives, what about the positives? What if this internship turns out to be the best thing you’ve ever done? What if it does lead you to wanting to stay there which then leads you to an amazing life that you love and makes you happy? Even if you stay here, you and your partner might not stay together and how would you feel if you gave up this opportunity and you guys break up 6 months down the road and you’re full of regret for not taking the internship?
If I were you I would 100% take the internship abroad, that’s an opportunity that the majority of people don’t get. Take it!
Urban exploring (for lack of a better term) with no purpose other than to discover. I live in a city and I’m constantly just wandering around going down streets I’ve never been down or into alleys I’ve never been in or checking out stores I’ve never been to. This is my approach when I travel to other cities and other countries too, I often don’t have a plan for my trip/vacation, I just arrive there and then start to wander and see what I find.