Rarely is dwelling on the past seen in a positive light nor should it be. Thinking too much about times gone by typically keeps your mind and life stuck in neutral and maybe even shifts it into reverse. If you habitually ruminate over your earlier life, you may regularly be revisited by feelings of anger, guilt, resentment, sorrow, or shame. Such emotions are hardly productive. In many ways, they're downright toxic. Fretfully obsessing about the people and events precipitating such negative feelings can lead to endless recycling. Becoming increasingly stagnant, or fixated, your thinking really can't progress toward any adaptive resolution.
Moreover, returning to the past to rehearse old dissatisfactions and grievances or even to replay images of earlier triumphs and idly preoccupying yourself with irreconcilable thoughts about them can result in self-reproach, lamentation, remorse, and even bitterness. Using your mental energy for such a doubtful purpose can catapult you into the inextricable pit of would have, could have, should have with the result that you can end up consumed with regret; which are most futile of emotions.
Yet, to be fair, dwelling on the past does have certain short-term advantages. For instance, you might become preoccupied with earlier events of success by way of rationalizing present-day frustrations and failures. If you haven't been able to live up to the hopes of others or to your own expectations, you might find temporary comfort in reliving past accomplishments. But while focusing on past positives may afford you some relief from current disappointments; by itself, it does nothing to direct or re-direct your efforts to further your objectives in the here-and-now. If you're to realize your full potential in life, you need to squarely focus on what you can do right now to fulfill your promise and not on what you achieved in bygone times.
Dwelling on the past can also be a way of not coming to grips with present-day realities. If your head is stuck in the sand of yesteryear, you may not be facing up to the fact that never having been this old before, you may now be less attractive, less strong and nimble, less quick-minded and adaptable, or with less stamina. There may be limitations and constraints that didn't exist earlier. The limitations that now need to be confronted and adjusted for and obviously, denying what in the past you may still need to make peace with can only hinder your moving forward in life.
Besides all this, loitering in the past can represent a kind of self-indulgence. It can interfere with your creating or in some alternate shape or form recreating past joys. Ultimately, it is pointless to employ memory to hold onto what may have been lost many, many years ago. As a result of not letting go of the past, you may rob yourself of present opportunities to reach out for what may still lie within your grasp. If past satisfactions and pleasures have left a vacuum in your life, now is the perfect time to diligently pursue what possibly might fill this void. If, because currently they're sorely lacking, you've been renewing in your head former attachments and endearments, you may be much less pro-active in searching out new sources of love and support than, optimally, you should be.