I can sympathise with the painful feet- I had been finding mine really painful, but found wearing orthotic insoles has helped a lot. Sometimes it's not always to do with Sjogrens, a lot of my pain was from Plantar Fasciitis. It might be worth trying insoles, you can get them from Amazon, they're not too expensive. Even if you can't find a cause, they're very comfortable!
I hate those days. You're feeling good, having fun and then BOOM! You hit the wall. No warning. And people don't get it. You were just fine 30 seconds ago and now you feel like you need to be carried out on a stretcher. We don't often have those good days where we feel normal like we can do what we need to do, much less add in stuff we want to do too. I think it the excitement that makes us ignore our bodies when they send the little hints and it isn't until they decide to give out that we realize we're overdoing it. That and we know if we stop long enough to take inventory of how we're doing we might not keep up the momentum so we just keep going. I've learned that if I have a really good day to set a limit and to be prepared for a few bad days to follow. It isn't as bad that way, but its still frustrating for me and my husband. He's really supporting nnd understanding, but sometimes the changes in my energy levels and moods is a bit much for him to believe I'm not making it up. Its hard for him too knowing there's nothing we can really do but let me rest and that sometimes I hurt too much to even let him hug me. So when he has those jerk moments of frustration and anger, its OK, cause he puts up with a lot. But the guilt knowing he is so understanding is tough too. He's not a lazy person. He's not good at sitting still. Thankfully, he's getting back into painting and I got him addicted to a game on his Kindle. We had to miss vacation this year, I had to use my vacation time prior to my short-term disability when I had surgery. So he's taking photos from past vacations and painting that.