Question: Despite knowing we cannot change the past, why do we constantly ask ourselves “What if”?
Answer: We turn to the past, regret the past, try to change the past when we are not satisfied with the present, when we fear the future.
If I was fully satisfied with my present state I would gladly accept, justify the past as whatever happened brought me to my present, perfect state. Then I would look at even the greatest past suffering as purposeful.
It is the same about the future. If I looked forward to a guaranteed, future, perfect state I would not worry about what I feel at present, how much effort, pain I need to go through to get there (for example going through a painful operation in order to become healthy). I would already enjoy and live in that future perfect state accepting my present difficulties, suffering as purposeful, necessary.
Thus all we need is a realistic, tangible, “almost there” future goal, optimal future state that can pull us forward making our past and present difficulties purposeful, positive.