Ever feel out of your body?

Like you don't understand how you got where you are or understand who you have become? It is so odd when this happens and especially when it happens during a great day, a successful day, a happy day. I have been noticing for some time now that wednesdays means two things for me: long, hard work day and the feeling above. It seems that the two are connected and I think in addition the feeling above is actually a form of anxiety. I can be totally happy and something will suddenly shift and I have panic feelings, or don't feel myself, or begin dissecting my life, interactions, and relationships. And then it passes just as quickly. Really strange stuff.