Why me?

I'm so tired of living like this.  I want to know why I've been so tortured my entire life.  Why am I so easily mad sad?  Why do I so easily become depressed?  Why every time I think about my past pets, especially those when I was growing up at home, do I get so sad and feel guilt for not spending more time with them.  I would give anything for one more day with every one of them.  I try to put into words the sadness I feel when I think about them and I just can never do it.  I think sometimes of the last time I looked into my boyhood dog's eyes, when I left to fly back to Atlanta.  I cried and cried when I left because she looked so frail and I knew it might be the last time I see her.  I cry because I wonder what she was thinking, wondering if she hated me for leaving.  She was my first real pet and she was so wonderful for fifteen years.  Unfortunately, I was not there for her the last four years of her life.  22 years later, I still cry every time I think about her.  See?  Here I am torturing myself over this stuff.  I should be over this stuff by this time in life.  Yet so many things from my life still just crush me when I think about them.  It's always been this way, so easy to get sad and so easy to get melancholy.  So easy to hear a song that takes me back to home and just fall down emotionally when I hear it.  I never wanted to grow up.  I just can't take all the memories.  Memories like this have sunk me into depression and sadness my entire life.  I just want to go back and live my life over again, basically doing all the same things I did back then.  I never got enough of anything.  I never experienced enough of my home or Buffalo.  I went away for college and was too busy in the summers to enjoy the city when I was home.  I suffered through three years of college where I was not able to experience any fun in the outside world.  I never went back enough to visit and have fun.  I married too young.  Now, I look back on 48 years of very little.  I've been able to do so many neat things over the last 25 years, but the only things that matter are the two dogs that I've given happiness to.  Other than that, I look back and wonder where the years went and why I let them pass so quickly.  I have little other than regrets to show for 48 years.  And now I'm too old to do it all over. And it's too late to start over.  What a fucking wasted life compounded by sadness every time I think of all the things I missed out on back home and all the past memories. I've missed out on so much.  High school friends that I haven't seen since high school.  College friends I've never seen since college.  A brother, and especially a sister, that I never got to become an adult companion with, feeling like a lonely, only child for the past 30 years.  You can't imagine how bad I wanted a sister to hang with.  Do you have any idea how it kills me inside to not have a sibling that I am even remotely close to?  I feel like a fucking freak.  And I think, "Where did the years go?". And how much more regret and sadness will I have in twenty years when twenty more years of distance from home have passed.  Again, I ask, why was my DNA saddled with this penchant for sadness over memories and lost opportunities?  I'm so sick of being sick.  I did not fucking deserve this in life.