To avoid over-ruminating about a decision, give yourself a time frame to think about it. 

If it’s a small issue such as what paint color to paint your office, perhaps a deadline of 10 minutes is sufficient; whereas a larger decision such as whether to accept a new job offer in another city may warrant a couple of days of thought.

To avoid thinking about problems all day long, schedule a specific time where you give yourself the freedom to think about the issue you need to make a decision about. 

If thoughts about the issue creep into your brain before your scheduled thinking time, tell yourself “No, I’m going to think about that after dinner, not during this meeting”.

Dwelling on a problem, thinking “this is horrible, I can’t handle this” or rehashing things that happened in the past are an unproductive use of your time.

Thinking about what steps you can take to improve the situation or actively thinking of a solution to the problem are helpful toward moving forward. 

Letting the inactive parts of your brain work through the problem can let the answer come to you when you’re not expecting it. 

When you find yourself overthinking about a problem, try moving on to another subject or changing your physical space by going for a walk, or moving your laptop to a conference room to work on something else.