Joseph's nightmare

Joseph's least favorite school subject is math. I'm not sure why, because he is good at it, and when I can actually get him to sit and concentrate for any length of time, he is pretty fast and seems to enjoy it.
Last year we would spend sometimes hours each day, with me trying to get him to do his math, having to sit with him and work through every single problem because if I turned away for even a second, he would sit there and stare into space and do nothing.
This year I compromised with him and told him if he would concentrate and have a good attitude and not waste time, he could wait and do math after dinner. He's been pretty good with this arrangement! Sometimes I still get a few grumbles, but overall, it is way better than it was last year.
Last week I was working on math with him on Tuesday night. It got kind of late, and he didn't get in bed until after 10:00. I was up finishing chores when I heard him come down the stairs. I went out to tell him to go back to bed, but he told me he had a nightmare, and asked if he could please sleep in my room. I told him to go ahead, and continued with my chores. A few minutes later, he came out of my room, almost in tears, telling me he keeps having the same nightmare and he can't get out of it. I went in to comfort him and gave him a stuffed tiger to protect him (I love that he still feels protected from bad dreams by a stuffed tiger!). He slept the rest of the night and I forgot about it.
Then a couple of days ago he reminded me of the bad dream and told me what it was. He was on a big soccer field and a giant number 3 and giant number 7 came running at him from either side, with a scary "Thum, thum, thum, thum, thum!" noise in the background. Just before they collided with him, he woke up. But when he closed his eyes again, he was back on the soccer field with the giant letters running him down.
Isn't that funny? I used to have nightmares when I had been up too late studying. I remember one vivid dream where I found myself amidst a giant organic chemistry model set, watching reactions taking place all around me. This dream scared Joseph a lot, though. I better not let him stay up too late doing math anymore!