I interpret this as maybe this is a day the way someone who is bipolar sees it? Since their moods change rapidly. If I'm interpreting that wrong, I'm sorry.

Or maybe just someone who is confused on how they feel... one minute they think they are happy and then the next feelings of fear and pain flood in from their past?

Either way, a good, simple poem. :) Like I said I like how you posted your older poems because I can really see how much you have grown from the older to your newer ones.