If you brush yourself off and keep pressing forward, you will learn something and you will earn another chance to get it right. Don’t waste your time being upset about something you can’t change. Start over right now, implement the lessons you have learned from your mistakes, and do it better this time.
Anyone can hold a grudge, but it takes a person with character to forgive. When you forgive, you release yourself from a painful burden. Forgiveness doesn't mean what happened was OK, and it doesn't mean that person should still be welcome in your life. It just means you have made peace with the pain, and are ready to let it go.