We should be sure that in our pursuit of happiness and positivity, we do not lose our ability to experience the other side of life, as well. Feelings of grief and respect for the departed, are honourable thoughts to have and honourable feelings to feel. In seeking happiness, we must not be so afraid of sorrow, that we lose the ability to cope with it properly. There is a healthy way to cope with both sorrow and joy; both need to be looked straight in the face, in the eyes.
A relationship between two people is made up, for the most part, of invisible things: memories, shared experiences, hopes and fears. When one person disappears, the other is left alone, as if holding a string with no kite. Memories can do a lot to sustain you, but the invisible stuff of the relationship is lost, even as unresolved issues remain: arguments never settled, kind words never uttered, things left un-said. They become like a splinter beneath the skin-unseen, but painful nevertheless. Until they're exposed, coping with the loss is impossible.