Jesus said, "Sufficient for the day is its own trouble," (Matt. 6:34). The wisdom of this can be taken in two directions.
An unproductive dwelling on the past keeps us from good focus on the work of the day. It will be useful for us to think about what Paul said, "Forgetting those things which are behind and reaching forward to those things which are ahead," (Phil. 3:13). Much time and energy needed for the day is wasted or lost, replaying past events. Often, we re-visit those events mentally but actually do nothing positive with that time.
Working Jesus' words in the other direction, the necessary attention to the current day can be hindered by a worry that tries to look too far ahead and anticipate all that might happen. If you can do something that should be done to prevent trouble tomorrow, by all means, make that part of the duty of the day. But treadmill thinking about all the possible trouble that might happen robs us of the productive attention the day requires.
"Today's trouble is enough for today," (Matt. 6:34, NRSV).