Being in the moment is a sure way to find happiness. Those who live in past cannot let go of the good time and the bad times. They live their life in the past over and over. Those who dream of a better future are always dreaming, and lack the action to solve today’s problems.
Obviously, overdoing anything can be detrimental. A certain amount of analysis is required to learn from the past, and a certain amount of planning is required to prepare for the unexpected.
Yes, spend most of your time being in the moment, because that is all you have. But pause in sufficient doses to reflect about the past and plan for the future. Reflection and planning are needed for self-defense and motivation.