Validating your partner is a skill that is essential to establishing and maintaining intimacy.  When you validate your partner, you are letting them know that you see how they are feeling, their feelings are important to you, and you are giving reassurance that they feel that way.  Everyone has a different experience, and those in distress may experience painful feelings for different reasons.  What is hurtful for one partner may not be the same for another.  Validating your partner is not the same as being in agreement, you can still disagree and validate.