To let go of someone doesn't mean you have to stop loving; it only means that you allow that person to find his or her own happiness without expecting him/her to come back. Letting go is not just setting the other person free, but is also setting yourself free from all the bitterness, hatred, and anger that you keep in your heart. Do not let the bitterness take away your strength and weaken you, and never allow pain to dishearten you; but rather let yourself grow from bearing it.
Don't let your heart run your life. Be sensible, and let your mind speak for itself.