You shouldn't have to feel bad for sharing your own personal experience, but I understand why you do. I think especially as we get older there is pressure to set a good example, and to motivate/guide others towards a better future, especially people who are younger than us. So being too honest is seen as a negative thing, due to the potential for influencing how others may perceive their own situation.
On the other hand, honesty is also important, and I find that being open about your experiences is truly the only way that others can ever begin to understand and take these matters seriously. Here is the only place I've ever found where I can be honest, and I don't think you should have to hold back either. Only individuals can make these decisions for ourselves about what we feel is worth it.
I feel very similar to both of you, I wish that I had passed when I was younger. I really started feeling suicidal as a teenager, but I was constantly told that life could turn around once I became an adult. Here I am in my late 20s now, in an even worse situation, but everyone seems to magically expect that people can turn things around on their own.
Since my teenage years, I developed chronic illnesses and pain. My ability to enjoy life is extremely limited by the constant experience of physical pain, and as I've gotten older, I just get to experience pain in new ways. The majority of the family members I grew up around have died, and I've had to witness so much sickness ravage people I cared about. Most of my close friends from university and such have moved on with their lives and seriously pursing careers, marriages etc now. There is 0 chance of me having children, and I've been in a couple long term abusive relationships now that have worn me out further.
I honestly don't understand what marvelous future people think is awaiting me. Being alone, and carrying memories of grief, isolation, pain, and so on, doesn't make me happy. Objectively, it would have been better off for me to have gone when I was younger, before I developed all these horrible conditions. While it's true that I've gotten to have some nice experiences like traveling, I honestly don't feel like it's worth it for me when weighed against the pain I am experiencing in daily life. It's been almost 10 years now since I first got ill, and my health hasn't improved at all.