I don't look at it as not letting go of the past. Good, rewarding and enriching friendships are timeless. Most freindships, tho, never pass the status of being mere acquaintances.
My spirital teacher, Rama, used to counsel us against forming close relationships, as in his opinion, most are not worth it. His favorite saying was...the going line for most relationships is not "what have you done for me"....but "what have you done for me lately?"