What do I need to know before flying alone?

I am thinking of flying alone to Iceland from Denmark on Christmas break. My mother will stay here since she will go in January. I have flown a couple of times with my parents
I flew from Zambia when I was 11, alone but the airhostesses helped me with everything.
Next we flew to Italy with mom and dad.
Then I flew to Zambia with my parents friend. parents remained in Iceland
Then last summer we flew to Denmark, all of us and dad flew again back home.
So now it’s time for me to fly to Iceland ALONE!
I am always scared when taking off…, but that doesnt stop me from flying.
I know all the checking in and stuff, but the thing that I am scared of is that Denmark International Airport is much much much bigger than the Icelandic one so that’s an issue already.
I want to take most of my clothes home and stuff.

umm…so could you just tell me what I should look out for and just what to do I guess…