Data from Fitbit can help you see patterns which otherwise you won't notice. I used to stay near a Railway Station, and my sleep used to get disturbed every 30 mins. I did not realize this until I saw the data from Sleep tracking. I was getting less than 50 mins of deep sleep and I could easily see that the deep sleep was disturbed at exactly the train timings daily. With this knowledge, I moved to a new place with less disturbance during night. Now my Deep Sleep is increased by 50% after this move.