In the mourning process the mind works through all of the connections that made up the relationship. You go over a myriad of memories and associations of the lost person stitch by stitch. It is both conscious and an unconscious work, it is a complicated and emotionally draining process.
On the one hand you find yourself looking for memories of the lost person, on the other memories come to you unbidden. They may come to you in a dream, or in a memory provoked by hearing a song or eating a mince pie. The memories come from everywhere and anything. This is the process of mourning, of gradually coming to terms with what has been lost, the work of saying goodbye.
You are going over all of your attachments to the lost person as you reorder the memories and associations to your self. It is as though the lost person is coming home to you, settling into your mind and psyche. They are gone, but not forgotten, and this is the work of preserving them deep inside you. It is a natural process that takes time to work through, no one can really say how long, it is a process that requires its very own sense of time.
This is deeply personal work, but it may help to tell someone about it, or it may help to write to a shared friend and tell them about it.
The dynamics of relationships endure. They don’t stop just because you did or didn’t say goodbye. But with death the possibility that you might one day meet and see that a former friend or loved one is ok is gone, and with suicide you know they weren’t. You are left only with memories, silence and grief.