I have not practiced in a long time, but the core idea of mindfulness meditation is to enjoy the "right here right now". If focusing on your breath isn't for you, you can focus on something else that puts you in that state, like closing your eyes and simply listening to the sounds around you.

This should help in quieting your inner monologue. When you find your brain trying to restart that monologue, just acknowledge that it happened and refocus. Remember not to think of these events as somehow being bad or failing since then you are dwelling on the past, just refocus without judging.

Edit: you may find this presentation that Jon Kabat-Zinn gave at Google interesting: http://www.youtube.com/watch?v=3nwwKbM_vJc

I also found his audio book "Mindfulness for Beginners" very enjoyable. The second cd contains 2 guided meditations which may help you get started.