Comfortable Ruts

One of the most comfortable emotions I've ever felt is the bittersweet feeling you getting remembering the past.  I say it's comfortable because it doesn't require any work to do nor does it give the expectation for more work.  I think about what was, what could have been, what I would have changed and how that might have affected those around me.  At times I get a little sad thinking about the past and I don't really understand why.  My life is great as it is.  I have an amazing wife.  I've got a good job.  I enjoy where I'm headed.  But there are still those occasional nagging thoughts that push through my present from the past, like flowers squeezing between cracks in the sidewalk.  If I had been better to this person, would they be where they are now?  They once said this to me, did they mean it?  Does anyone else think about those experiences or am I the only one who hasn't seemed to move on?  How much of an impact did I have on their life?  When we knew eachother, was I important to them?  Did they value my friendship?  What changed?  Pestering, nagging thoughts that I'll never be able to answer, partly because I'm afraid of the answer.  If I really am the only one who has these thoughts, who remembers how friendships used to be and longs for that connection, coming to that realization would be crushing. And isolating.  The past is static and I know I cannot change it, but I, like a wool sock, seem doomed to cling to it.