Relationships come in all shapes... friends, co-workers, chums, blokes, dudes, shopping partners, party cohorts, and lovers. They are all different. But they are also very similar. They take time and nurturing and kindness and love. The rewards can be overwhelming and life fulfilling.
But on the other had, if you do not "feed" the relationship or the other person fails to "feed" the relationship, the relationship withers away sometimes slowly at first. At times, you don't even see it until it is too late. Sometimes, so quickly you weren't even paying attention... But always know this, you can save it... but it must be before you let it whither away. Once it has died. It may be far too late.
But when, and if it gets turn around, and the relationship is feed and nurtured and loved and respected, it can truly begin to bloom again. Not as before, never as before, but maybe better… even stronger. Like a bitter cold winter and the plant that comes fighting back in the spring within inches of its life. Those are the ones that last... endure... survive. It is up to you sometimes.
Other times it is completely out of your control. Don't fight it if it is not to be though. If it has died... bury it... find closure... you have to, or it will eat away at you. There will always be new people in your life. Learn from your past, be in the moment... and build for your future. Don't check out... check in... be there... and there will always be someone there for you.