Time goes in one way, so life is just a series of NOWs. At some point they all pass, and are all in the past.
So though the past does create you, what if you couldn’t actually look back on it? A short relationship with someone or a long one would make no difference at all. They may have shaped you differently, but still grieving over the loss of a long one or a short one would be a complete waste of the one thing you can not get back –time.
It’s also why, after the griveing process, lamenting and regret is a waste of those NOWs. It’s a waste of your time and also of your life.
So if this NOW sucks, change it. And if this NOW rocks, embrace it and pay close attention to the person/people creating it, your feelings, the sounds, the smells and everything that make it up. ‘Cause eventually (soon, in ages, who knows) your NOWs will run out. So make them Good ones.