In retrospect
Definition 1 of 1
Pro Tip 1/3Past Reflection
Used when reflecting on the past with a new understanding or insight not recognized earlier. 
In retrospect, I recognize that the advice she gave me was really wise.
Pro Tip 2/3Implicit Regret
Often conveys a sense of regret or a realization of a mistake, even if it's not stated explicitly. 
In retrospect, attending that event wasn’t the best use of my time.
Pro Tip 3/3Emotional Insight
Can indicate an emotional or intellectual change in how one views a situation. 
In retrospect, I understand why he reacted so strongly.