The Five of Cups speaks about regret, and remorse over severed relationships or an unfulfilled dream. We all at one time or another live with regret, saying to ourselves "If only..."
We don't need to focus only on what is spilled. There is still one cup that remains, and it is upright, so all is not lost! There is always hope!
We can't hold onto regrets, because it is living in the past, and this robs us of today's happiness.
There is nothing we can do about what has happened in the past, other than makes amends, if we need to, and ask for forgiveness. We also can make the effort to not repeat the same behaviour, or make the same mistakes.
Usually people will forgive if we are honest, and have a sincere heart. We forgive others that have hurt us, for ourselves, not for them, so we are not carrying around resentment, and bitterness, that eats you up inside, where a bitter root grows, with bitter tendrils like vines that invade, and enter every aspect of our lives.
The hardest thing is to forgive ourselves, this has always been my experience. Accepting and acknowledging that we have done wrong to the person we have hurt, including ourselves, enables us to move forward, to make a new start, and strengthen our relationship with ourselves, with others, and with the God of our understanding.