Going back as far as I can remember in my life, I think I subconsciously knew my emotions were "off". I can remember certain times when I would have an emotion that actually caused me physical pain. As a child growing and learning, just like with all things, you learn what is normal and acceptable and what is not. I knew my emotions weren't normal and acceptable, so I had to outwardly fake things to appear normal. I buried the pain, sorrow, anger, hatred, etc. deep inside. Happiness and excitement were no better. Largely because once I hit a "high" with something, the next time had to be vastly "higher" or it just didn't have the same impact. It would become flat. For example, if I got a great birthday present, the next year the gift had to be bigger and better.
So as the years went by, my highs got higher and my lows got lower. To some extent this happens naturally with everyone I think. I've tried to describe it before like this: a toddler gets a new toy and they are ecstatic, but take that toy away for even a minute and their entire world crashes. Why the extremes? They don't have much life experience at the point to gauge their highs and lows on. Comparatively a normal adult gets a DVD they wanted and they are happy. The DVD gets lost or broken, the adult isn't happy, but their world doesn't crash around them like the toddler with the toy. The adult has had more life experiences to put things into context. An adult has experienced things like marriage, child birth, death, graduations, promotions, etc. that has developed their emotional range.
Because of my mental illnesses, my range of emotions got perverted as I grew. For me personally, there are many different factors that affected my scale. For example, emotional abuse, alcoholism in my family, sexual abuse, trauma, chemical imbalances and such. By my teens, my range was so vast that a good event in my life barely pulled me up past the half way mark. Life became darker and more pointless. I was fifteen when the depression finally took over and I succumbed and had a complete emotional collapse. Everyday was worse than the day before. When nothing can make you feel happiness anymore, that very fact makes every moment of your self slide further and further down the emotional scale. You eventually realise their is no bottom. It's a bottomless pit and the walls are greased. No climbing back up.
It took me literally decades of therapy, medications, hospitalisations, and self reflection to rework my emotional scale. It's by no means "normal" compared to the average, but it's nowhere near as vast. That's not to say I've magically erased all the bad from my past. It's still there and so are the low points on my scale. But I've learned to live in a narrower range. I've even managed to up the high side which not even seven years ago I thought would be impossible.
I try live in what I refer to as the "content" range. It's still a lot wider than most. Just ask my husband, he deals with my wack-a-doodle ass everyday. But I've gotten much better at realising when an emotion is an overreaction. Sometimes it's not exactly in the moment and I have to back track and make apologies for ridiculous responses (once again, talk to my hubby), but the fact that I can recognise my irrationality at all is amazing to me. So I forgive myself when I'm overly emotional and say or do things that hurt others. And I make apologies when necessary. I allow myself to have bad days, but have my depression combat kit at the ready with all the tools that help me stay in my "content" range. I've also surrounded myself with loving and supportive family and friends. Those closest to me know my story so are able to help me regulate when necessary.
Living with a skewed emotional scale isn't easy. But with support and effort, it is manageable I've discovered.