Does it mean that you've lost control of yourself that you'II do things you didn't mean to do?
In short, yes.
It's a turn of phrase that means you got completely wrapped up in the activity.
Usually it's used as an excuse as to why you're late or didn't get something done!
[Sorry I didn't do the work/ Sorry I'm an hour late] I got carried away playing WoW.
Or it can just mean you went too far with the activity (because you were on a roll or just enjoying it too much.
Sorry I went a bit over-board on the decorations, I got carried away.