When you cant stop thinking of the past today, look at why this might be and resolve old issues.
You will find your mind wandering to the past all the time today and though you may be perplexed by this, the answer is within you. Theres likely to be a reason why your brain is stuck looking backwards, and once you pin point what this is you can start to resolve it and move forward again. Anything you have not dealt with from your past needs to be sorted out.