I have had the same experience with unpredictable mood/emotional starts and stops, to the point of it controlling my daily feeling/activity more than I've wanted. I've felt many a time very isolated, thinking there's no way 'normal' people experience these same ups and downs. And I suppose that is the point. What is your reference for normal? And why is what is normal necessarily good? I've been trying to change my reference point. I've been trying to stop forcing myself to act the same way everyday. Each day is new, you are a different person every time you wake up. It can be scary from the standpoint of thinking that you don't have an identity, or, if you prefer, you can approach it as an opportunity to grow. I try to think of it this way, its not your emotional response to external stimulus which defines you but the way that you approach your emotional response to external stimulus, and separating authentic emotions from emotional responses to external events. In some situations a rational analysis of your response is warranted, ie do I have control over the events which are causing me stress or anxiety, if there is any thing I can do about it then do it, if not, you have to realize that its out of your control.
That said, in general, my main goal is to live authentically, yes broadly used and thrown about in certain corners of the universe, but nonetheless the most accurate representation of my inner desire...obviously this leads to existentialist philosophy, one which I find helpful is Heidegger's concept of angst. Where he says that angst in one's life should be used by one to examine critically how they are living their life and whether they are living according to their own expectations or to the expectations of others (be careful of people summarizing philosophical positions in one sentence).
And so...I try to live out of phase with everyone else, like two sine waves that every once in a while come back to meet, but the rest of the time are on their own trajectory. Works well for me because I can very easily become hyperfocused on whats going on around me, and I honestly don't need to be that way in general, as it is a source of anxiety. Stay focused on the bigger picture, and realize that other people are different and you won't relate to them much nor them you...and embrace your moods, at least the authentic ones, because they are probably telling you something about your life that you may not have realized before.
Hoped some of my rambling helps,
Best