I have every reason to be sad, but I don't have any reason to mourn. People grieve when things end. Nothing has ended tonight. One of us has simply gone ahead as we always knew it would have to be.
If we accept time for what it is, how it flows and how we flow with it, I doubt very much that we would continue wasting loads of it by constantly checking our watches. The gnomons's shadow falls where it falls - and so do we. Where we are now is where a lifetime's worth of steps have taken us.