Have you ever had a case of the "what-if's," or, as they are sometimes known, the "if-only's?"
Dwelling on the past serves no purpose. The past cannot be changed. Dwelling on what could have been or might have happened if we had lived our lives differently is really just a waste of energy.
I find myself doing this at times. I think about what might have happened if only I had been more dedicated to my writing when I was younger. Or, what if I had finished college? I could have accomplished so much. That type of thinking cannot and will not change a thing in my life today, and it will certainly not change the future.
Instead, what I need to do, what we all need to do, is focus our energy on the here and now and what lies ahead. We need to the the things that we can do today to make tomorrow better than yesterday. But, we can't be overly concerned with the future either. Jesus said that we shouldn't worry about tomorrow, for tomorrow brings its own worries (Matthew 6:25-34).
We need to focus on today, doing what the Lord guides us to do, seeking His face, and living righteously. When we forget the past, focus on today, and avoid worrying about tomorrow, the result is greater happiness.