Telling someone to "get over it" doesn't sound like the most kind or helpful advice. Obviously it can sound dismissive in tone and make someone think that you simply don't care about the way that they feel. There is great truth in the principle behind it however. I've learned that sometimes it's healthier to use that philosophy instead of holding on to our emotional wounds.
When we refuse to let things go, we will permanently damage relationships as we become collectors of pain instead of being distributors of mercy. We even do this with small things as they pile up and become collectively more poisonous than they are individually. As harsh as it may sound, we need to learn to let some things go before they destroy our relationships and erode our emotional and spiritual health.
Decide to exercise a statute of limitations and let some things expire that need to die out for the sake of our own survival.