Someone showed me this a few years ago and at first I couldn't do it. I practised for a while and can now do it easily. I know a couple of drummers that can do it as well. It's not that it's not impossible, it's a psychological thing. I get it a lot when I'm playing music. I know what I want to do but my hands won't do it and it takes me ages to break the barrier.
Keep trying, you'll crack it eventually
