Pain is a really interesting thing, and there's an undeniably subjective aspect of it. My wife has had a chronic pain condition since 2008, and one thing I've noticed it's that her pain is worse when she's stressed, PMSing, or whatever. There's no objective way to measure pain, and I think at least part of what's happening is that her ability to deal with one level of pain gets better or worse depending on her mental state.

I think of it like going out and finding you have a flat tire. If there's not much going on, you're not rushed, you had a good night's sleep, etc., you might just think "Well, that's annoying," and deal with it. If you're sleep deprived, your kid is sick, and you're under a bunch of pressure at work, you might just want to sit on the curb and cry. Same situation, but your ability to deal with it is different.

Pain is like that, I think. If you're in a bad place, things seem to hurt more because your ability to deal with the pain is less.