Chronic pain is an entirely different beast from acute pain.
Unfortunately, whatever caused the arthralgia was (and still is) a complete mystery, and by day 5 of having top pediatricians explaining "nothing is out of the ordinary" I pragmatically, unemotionally contemplated suicide for the first time in my life. Somehow the ailment completely disappeared over the following weeks and hasn't returned, but it's quite something to feel that pain will truly and honestly never stop. It's not even that your brain goes into panic mode. It's a different mode of existence altogether – I can't even imagine people suffering through years of pain even 1/100th of the intensity of what I had.
It isn't easy. The pharmacological therapies I know would be most effective are too expensive. And so I have to choose how to avoid suffering from my pain, every day. I choose work, music, my family, antidepressant and anti-anxiety medication, and participating in communities (like this one) where I may find peers.
[0]: https://en.m.wikipedia.org/wiki/Ankylosing_spondylitis [1]: https://en.m.wikipedia.org/wiki/Psoriatic_arthritis [2]: https://en.m.wikipedia.org/wiki/Anterior_uveitis [3]: https://en.m.wikipedia.org/wiki/HLA-B27
Humans are very often disabled by pain alone, with neligible body damage. That's clearly evolutionary disadvantageous. Makes torture possible, etc.
Relevant xkcd: http://xkcd.com/883/