We can think about the future and the past but we can only act today. The only way you can change the future is through what you decide to do today. You should focus on today, even when thinking about the past or planning for the future.
No matter how you feel about the past, there is never anything you can do to change it, except as far as you change what you are willing to do today. You can and should identify past mistakes because it means you have learned from them, are less likely to make them again, and have greater wisdom to help others avoid the same. Realizing something you’ve done wrong in the past gives you the opportunity to do what you would not have otherwise done now.
There are always things about the future that you can’t do anything about. However, there are also always some things about the future you can do something about. You should focus on today, even when thinking about the future. It is good to consider the future in terms of what you need to do today to effect desired outcomes. Focusing on future events outside of what you will do today won’t help you.
When we incorrectly focus on what we can’t change instead of doing what we can, we generate unnecessary mental and emotional turmoil as we dread or delight in what might never happen. You will experience greater relief as you correctly parse out the things you can change from the things you can't change. When you list out these things, on paper if need be, and isolate the specific actions you can take to work on the things you can change, the likelihood that positive anticipations will actually occur, and that negative anticipations will abate.