After some pontification, I've concluded the reason I don't stand up straight when I skate is that I'm afraid of falling back onto my head.
Initially when I started skating, I was really scared of falling backward. As a kid I had an off-ice injury where I tripped over a mat and fell right onto my tailbone (probably fractured but the doctor didn't want to do x-rays; it was very painful anyway). Other than that I had no other experience of falling backward in my life at all.
Inevitably I eventually did fall backward in skating and realised that not all backward falls are right onto your tailbone, and in fact are generally less painful than forward falls onto the knees.
However, I've seen a few bad falls with people falling back and hitting their heads, including once when I was on a public session and a kid had to be taken to hospital as this happened and he couldn't walk afterwards.
So now I have this fear of hitting my head on the ice (and also the barrier; I hate skating near it unless I'm holding it). When I fall I tend to crumple forward and land on my backside. But I'm convinced that if I stand up straight, I'll tense up in a fall, my shoulders and hips will lock and I'll fall backward onto my head. Like, if I'm not already leaning forward, I don't think I'd automatically do so in a fall.
I'm not sure what to do about this. Is the scenario I've described likely? I mean, obviously there must be some way to fall from an upright position without whacking your head, or all skaters would go around with permanent concussions. But whenever I stand up straight, I feel like I'm going to a) fall backward and b) tense up and land on my head.
Thanks for any help!