While it may be unfortunate to some that we cannot go back in time, be grateful that this dimension cannot be re-entered. Your ignorance and narrow state of mind would be reclaimed. Superficiality restored. Priorities unfocused.
As time goes by, a better version of yourself is always in the making. Why return to situations of your past? So you can make them better? You simply cannot go back in time with the knowledge you currently have to re-live and formulate a better outcome. That experience gave you the wisdom and knowledge you currently have; and attempting to receive a new lesson out of it would be selfish. Remember that the universe already knows your path and your purpose; it already knows the lessons and obstacles you need to face. The tests have already been written out for you.
This is why I say time is on our side: it gives us a one way path that pushes us forward, forcing us to focus on what is next, rather than how can we go back and have that same experience again.
Appreciate the obstacles and challenges in your way, they are building you up for greatness.