"DON'T CRY BECAUSE IT'S OVER, SMILE BECAUSE IT HAPPENED" - Dr. Seuss
This quote can be applied to so many different situations and whether a relationship has ended, a friendship has broken, you've lost someone dear or you're experiencing some other form of emotional distress, it's a reminder not to reflect on what you have lost but be grateful for what you had in the first place.
Smile because it happened, learn from it and look forward to the future.
Things end, life ends...... it has to as it once began but it doesn't mean that the journey in getting there was meaningless or pointless. Everything in life happens for a reason.
So, make the best of everything, live every day as if it's your last, hold on to memories, remember the good times and be glad that it happened. Don't waste time in crying over the ending.