Speaking My Mind

We are all very good at telling what states of mind we are in at a given moment. When it comes to our own present states of mind, what we say goes; an avowal such as "I'm feeling so anxious" or "I'm thinking about my next trip to Paris," it is typically supposed, tells it like it is. But why is that? Why should what I say about my present mental states carry so much more weight than what others say about them?