Sometimes when i have a lot to do during the day, i can't focus on one thing, especially if it was reading. When this happens, i speed read, and don't retain anything.
To help, i stop, relax, and try to figure out why im racing so much. I tell myself it doesn't help me or benefit me in any way to speed up. And, if this doesn't work(i don't expect being rational to fix things all the time), i put the reading down, and do the chores, jobs, etc, that are causing me to get anxious.
Your problem might be a little different, but thats what happens to me.