A little zen-ish or not but you can not go into the past and hit yourself with a hammer or unhit a hammering. You can plan to never hit yourself with a hammer at any time in the future. But right now the exact present is the only time you havve control over the hammer, you can pick it up or not. Planning to never hit yourself with it in the future is the plan, to never pick it up in any 'now' is the way to get there.