This is true in my experience as well. It feels like there's a limit to what people are willing to hear, and over time compassion waxes and wanes. For some people, I understand that it is stressful or taxing to be confronted head-on with the suffering of others, and they seek to avoid it if they feel as if those uncomfortable circumstances go beyond a temporary matter.
But it's just so lonely if you're the one with long-standing problems, and no where to go with them. A lot of friends are fair weather, and might not even want to hear about things a single time. I learned this lesson the hard way.
Throughout the years, I've opened up to loads of people about various things that happened in my life, from my chronic illness, experiences with abuse, SA, struggles with work/school, and a lot of people turned my suffering into a joke, acted dismissive, or wanted to make a competition of who has it the worst rather than being supportive.
I learned people only really liked me when I was playing the role of the funny person telling jokes and providing them with entertainment. Whenever I became more quiet and withdrawn, even though I hid my inner demons and issues from others, I immediately got abandoned by everyone.
Social games seem to be dictated by whoever can put on the most peppy, energetic and positive personality. Which I find incredibly exhausting and unsustainable.