I don't think it's uncommon for the diagnosis to change. But like you said, there is no sense in giving label's power.
If someone said you were bipolar 1 and someone else said you were bipolar 2 and someone else again said you were neither... it isn't going to affect your mood's in the future- what'll happen will happen no matter what label you put on it.
I'm not too sure what a mixed episode consists of exactly, but your doctor should be able to tell you more about
that. I say it's wise to just take one day at a time. If it so happens your irritable today then you can try and see it through knowing that it wont last forever.
Remember the last thing we feel like doing when we're in some negative mood is the things that help us...like exercise or taking a walk or talking to someone. If you can try and keep making progress it makes those negative moods more managable. Good luck tomorrow