When I was really unstable, I still had some periods in between -however short-lived at times- when I was 'normal,' meaning not in the throws of an episode.

For example, right now I'm very sad that someone close to me has passed away and which has also brought back some terrible memories related to the war-torn country I lived in (because that's where he lives). I've been, at moments, overwhelmed by these memories and the sadness.

But all of this are normal reactions to the circumstances; though this doesn't make them any less difficult to deal with. It just means I'm human.

So sadness and feeling overwhelmed can also be 'normal' in that they are natural reactions to my circumstances.

I don't think 'normal' necessarily means happy or even contented. Just that we're not in the throws of an episode. And unless you're super rapid cycling that means that you have some 'normal' in between, however short-lived, and I think everyone's normal is different and can also change depending on the circumstances you're in.