Our lives are built upon a foundation of balance. Everything we let into our private psyches affects us, but did you know that each circumstance in your life is dependant on the other? We are part of the whole, and this is reflected in each aspect, large and small.
Our emotional balance depends on so many details ... minuscule matters such as how you awake in the morning, whether you drank coffee or tea, what the weather is like, the moods of the people in your home, and countless other circumstances. There are of course bigger things that affect us as well, such as an argument with a loved one, a close friend moving away, someone close to you being sick, and many many others.
In light of these revelations, it is important to recognize that our emotional balance varies from day to day. There is no reason to be hard on yourself for not being as happy as you were the day before. Be gentle with yourself, and continually recognize that you are an emotional being and that things affect you. There are many books, movies, songs and poetry about remaining positive, but I believe that sadness performs a purpose. Sadness give you an opportunity to become an introvert, focus solely on the feelings and then release them. You can use your emotion to purge your negative feelings, and to essentially make room for more love, more happiness and more peace in your life. It is okay to cry. It is good to cry.
This reminds me of a Holly Cole song called "Cry if You Want To" ... Enjoy!