I'll be very upfront and personal here. I've gone through a divorce, and that separation was almost worse than a death. I have lost close friends/family as well. In death, often times there's some type of closure. Sometimes in divorce there is as well, but sometimes, as in my case, there is not. There's almost a fear of seeing him again, though I once loved him. It's a strange feeling that I don't wish on my worst enemy.
You may be sad because a friend moved away, or you moved away. Maybe you hope you will still stay in contact, and maybe you will. But it won't be the same. It's almost as if that person is dead to you. It's a form of divorce, or separation.
When I mention a change in lifestyle, maybe you have become more financially abundant, or maybe your friend has. Maybe you have become less financially abundant or a friend has. It could also be that you're not smoking, drinking, or doing drugs anymore, and now those friends are as good as dead to you. You want to still be friends, but you don't want to do what they do.
Whatever the reason for the feelings of grief, one of the first best steps you can take for yourself is to allow yourself to feel it. Whether it's sad, bitter, angry, hollow, nothing, shock or some other feeling entirely, focus on that feeling and allow your body to feel it. No matter what society says, it's OK for you to feel. It's healthy for you to let it all out, without destroying things, of course. Allow your body to feel these sensations. Allow your mind to think those thoughts. Allow negative emotions to drain out, if you choose. Write poetry, be by yourself, talk to a friend, take a walk. Do whatever will help you feel those emotions. It is by allowing yourself to feel the emotions that they go away. You may choose to savor the moments while you can. It is when your bottle up your emotions that they linger.
Let it go. It may not be easy but, let it go. I'm sure you'll feel better.
Life and Corporate Coach