I'm with you on this one! Used to be like, yay! I feel great again, and now I'm like, oh gosh, am I crazy!? I suppose being like this also has it's advantages! We shouldn't think of ourselves as less valued because of this, of feel bad for feeling good. It's what it is! Of course the goal is to be stable eventually though, probably makes a lot of things somewhat... easier

A mixed state is feeling both up and down at the same time, could be a feeling of anxiety, depression and agitation. Think I had that a few days ago as a reaction to Saint Johns wort for like two days, before it leveled out in hypomania...
There's a really good website that has a lot of ( slightly more scientific, but written in a nice way ) information on bipolar : psycheducation. org
Also check out the information on light, darkness and why it is so important! I think we can keep ourselves way more stable with proper darkness at night and good regular sleep. (sounds easier than it actually is, I know! but still )

Good luck with your information search!