I have been choosing a word every year in the 'One Little Word' style. I don't do anything formal with it, but I keep that word in mind as I go through my days/weeks. I find it really helps. Perhaps you can choose a word that reminds you of how you want to feel.
I need to work on my negativity a little myself. I am positive and happy around strangers but my closest friends and family get the not-always-so-happy me and they probably think I'm negative all the time.
