And now, in total contradiction of my previous post, I offer this phrase, which has come out of discussion with others facing difficult circumstances that leave people at a loss for appropriate responses:
Say nothing. Do something.
People don't mean to, I know, but they often say irritating things when they're trying to be helpful. In my experience, few words help but what does make a big difference is action, as noted before. The meal dropped off, the provision of babysitting at a moment's notice, the pop-up picnic...the list is endless.
So if you feel words catching in your throat, you might want to check them before they come out of your mouth. Put your hands/feet in motion instead. Even tiny gestures can make a big difference.