You need to remember that you work for the FACILITY, not the individual unit. Management is responsible for running the whole facility, not just one unit, one unit, one unit, etc. They have to do whatever it takes to run the whole facility. They know floating is not terrific for pts and staff, but options are limited (just remember when your unit is short, someone else was floated!)
You just do the best professional job you can. As time goes on, you will most likely be floated again. Your being a newbie, I can understand your anxiety. It's obvious that you want to do good care. I'd bet that you did fine when you did float that time.
As much as I dislike being floated, I remember my paycheck is signed by XYZ facility, not east wing or 6th floor.
It does get easier. In fact, I actually was a floater for a while - I LOVED IT! Staff LOVED me too, as I was the extra person. I went in to whatever unit they gave me. Did my job; didn't get caught up in the floor drama, worked well with the regular staff, went home on time, etc. Unit mgrs even put in requests for me. I had my favorite floors, and there were ones I DID NOT like (because of ding-a-ling staff). As you mature, you'll see!!!