As A.E Housman put it in the poem "A Shropshire Lad XL":
That is the land of lost content,
I see it shining plain,
The happy highways where I went
And cannot come again.
One of my favourites, as it describes the bittersweet longing for people and places you once knew but you cannot revisit or come back to (and even if you did, they would most likely have changed beyond your recognition). I often feel nostalgia for the years I spent living abroad in Latin America, the friends and relationships I had during that time, the long nights spent with friends and girlfriends in seedy dive bars with sticky tables, or picnics on hillsides beneath the starlit sky, amongst a million other great moments, but I think the key to overcoming nostalgia is to make peace with the knowledge that "what you had, you had". People and places change over the years and time moves on; from personal experience, I typically find myself wallowing in nostalgia when I have insufficient things going on in my present nor plans for the future, so it's important to try to set meaningful goals and try to meet new people to form meaningful relationships with. Just my two cents anyway, hope that helps, buddy 