I think you're approaching this in the right way. You know that logically it's not worth your time to dwell on something you can't change, but knowing that doesn't change how you feel about it, because feelings aren't rational.

You can't make the feelings go away, but you can find a better way to express them. You came here because you needed to talk about your feelings, and that's a good start, although in general the internet makes a poor therapist. I would recommend starting a journal, either on paper, in text, or using a voice recorder, whatever feels most natural. Journals are good listeners.

Pay attention to yourself. Allow yourself to recognize your emotions, and how they affect your body. Listen to your breathing. Put a finger on your wrist and try to feel your pulse. Take a moment to be aware of your hunger, your thirst, your aches and pains, and how all of them feed back into your emotions. Work with your emotions, not against them.