To validate is to prove that something is based on truth or fact, or is acceptable. It can also mean to make something, like a contract, legal.
You may need someone to validate your feelings, which means that you want to hear, “No, you’re not crazy. It’s acceptable to be angry about that.” Or you may need someone to validate your parking ticket — which means you have to prove that you bought something, so you can get parking for free. Whatever it is you are seeking to validate needs the added support or action from someone else to make it valid.