Is My Mind Full Already?

On my way home last night (a long 3 hour drive) I listened to a talk about Mindfulness; unfortunately the talk didn't explain much about what this is rather it focussed on reminding oneself to be mindful and using triggers throughout the day. I suppose that being mindful is about actively thinking about how you are, about how you react and how you feel...being "purposely aware" of your actions. The person on the talk I was listening to, referred to being awake; awake to your thoughts and actions. So, when I was washing the dishes from our evening meal, I tried it out. I didn't manage very well and my thoughts probably wandered...I say probably as I can't recall at all what I was actually thinking. Is this a case of must try harder or is this a common experience I wonder. I will keep trying, especially during meditation but I suspect it's much easier then.