Yep I agree, longing for the past can definitely hinder your ability to experience new things. In fact there are some cases where people may be afraid to make new memories because they either don't want to forget about the past, they may also be afraid to experience joy knowing that one day they will look back and wish for those days again once the people they made the memories with are no longer around.

I think there's an actual name for that where people are legitimately afraid to be happy and experience joy in the event something bad will happen in the future but forget what it's called, I know it prevents people from engaging in activities that may be fun and make new memories. In a way it's understandable because during the rare chances I am enjoying something, in the back of my mind I know that the feeling of joy and being in the moment having a good time will not last very long so I can understand being afraid to be happy.