I'm very similar, and most of my life I have hidden my more sad, negative side. It makes me feel genuinely better that people like you exist. Because half the reason we are so miserable is because we know we are miserable, it's intricately attached to our identity, decoupling it from all our reasoning to see the brighter side of life isn't a switch that can be instantly flipped, and it requires trust between people who won't judge us for not having the energy to fake a smile when we can't.
The power of positive thinking can be destructive if it has been automated. Negative thinking can be the same way - it can be automated, although from my experience, my negative thinking usually helps me see flaws in my own reasoning to such excess that I don't feel I'm at risk for it being automated without being able to reason myself out of whatever is automatic.
I'm glad you are thoughtful enough (and that's not meant as a back handed compliment, abstractly positive thinking and negative thinking function the same way, they just interact with different components of self-social systems) to see things in less simplified ways. I have one friend who is like you, and it's constantly a struggle to override my belief system that they are sick of me. But that's the automatic thinking spiral I get stuck in. And I would think most people who are cynical like that think similarly, because that's what we are used to. Emotional vampires, black holes, draining. All those pejoratives affect our self perspective.
We don't know how people will judge us. It's nice that people are willing to speak from another perspective. Positive thinking, from when I've experienced it, can feel very group think, like, everything will fall apart if you stop thinking that way. That is such a suppressive ideology to me, it feels dangerous, and I'm not comfortable simply allowing myself to be one directionally convinced into thinking that way. It doesn't take my perspective into account.
So in the end, I find, the people who can handle interacting with me and staying positive have very strong minds, both intellectually and emotionally. And they demonstrate that there is a brighter side to life that doesn't imply we're all going to jump off a cliff because it's fun, and not see the ground coming. Sometimes bad things happen in life. It can't all be controlled by attitude. There are real things that happen in life that affect emotions. Forcing oneself to pretend everything is fine is suicidal.
I'm not used to being happy. It makes me uncomfortable often. That doesn't mean I fear it. It just means I have to be very careful in experiencing the emotion. Sadness too. Sadness over things that make you sad shouldn't be suppressed, nor should it be attached to people like 'those people made me sad'. That's just going to hurt a person in the long run, because sadness is an awareness. You need sadness to know happiness. Suppressing emotions leads to convoluted reasoning, missed connections, insight and clarity into one's own circumstances, real things.
I feel neutral talking to you, but I feel better in general knowing most of humanity isn't on a collision course to remove half of it's emotional reasoning away.