Some folks will put about a hundred times more mental energy into lamenting the loss of something than it would take to either get it back or make a new one.
There are a very, very small number of “once in a lifetime” things. Most things you value can be repaired or replaced – from favorite mementos to interpersonal relationships. Either accept that it’s gone and move on, or work to undo the damage caused by its absence.
But sorrow will carry you down with it. Shed, and move forward.