Yeah, don't be too hard on yourself. Mindfulness takes some people, whose only job is practicing mindfulness, a lifetime. Monks and the like.
Some people just aren't cut out for that NOW way of thinking. You almost have to already be fairly calm and centered to master it. The zingy, type A, hyper-scattered person can probably still benefit from attempts, though.
I'm curious as to what you intend to gain from this way of being?
If I think about how I think, I'm pretty sure that I have more gaps in my thinking than scattered thoughts. In essense, I can have out-of-control thoughts but mostly if I am not focused on a task, my mind naturally defaults to a blank state or "wait" mode, like a computer that isn't being tasked. It's obviously still working on things on some level, but not bouncing all over, randomly. I'm not sure if that is a good or bad thing. But it's certainly not annoying, I can vouch.
Jennifer