Recently during my meditations I have found the words past and future to be helpful when I find myself thinking instead of meditating. I just look and see what I’ve been thinking about and determine if it is a past event, something from my history or a future event, something that hasn’t happened yet. By doing this it immediately brings me to the Now and reminds me that I am meditating not thinking.
During meditation your mind is clear and relaxed so it is the perfect place to brainstorm up an idea or think about a subject that has been troubling you. So as soon as those ideas come into my head I name them Past or Future, and I again remind myself that I am meditating not thinking.
Try it and tell me if it is helpful.