Haunted by what I dont need

I feel the need to journal right now and people are on my mind.  People are almost always on my mind.  Their voices haunt my thoughts, and tear at my desires.  When I hear a group laughing I automaticaly yearn to be there, sometimes even when I'm with another group...
but why is that? Why do i always feel like I'm missing out, like everything good is happening somewhere else?
Is it because I am not content?  I think at times that is definately my problem as much as I hate to admit it.  It seems like I am stick in this contunous cycle where I realize my discontentment and challenge myself into fixing this problem and eventually I lose that self-awareness and slip back into it.  I'm not sure how to break this cycle but is is time to banish discontentment yet again.  It is time to savor the time I have and the friends I spend it with.  I do not need anything more, and what I already have is way more than I deserve.  I will no longer be haunted by the thoughts my mind conjures up to convince itself that the grass is greener in another group.  This not going to be easy, it requires a war within my mind, and yes I will be tormented but I need to win contentement, I must win.  These desires of mine cause so much unnecessary worry or stress. 
How do I implement strategy? I guess its a conscious decision every single time to remind myself that what I have is more than enough!