A study finds that positive events outnumber negative events and that we therefore use far more positive words than negative words:
The researchers say we've adopted a number of habits of convenience that reflect the frequent use of positive words in our language (in turn reflecting the greater frequency of positivity in the world). For example, positive words tend to be 'unmarked' - that is, the positive is the default (e.g. 'happy') whereas the negative is achieved by adding a negating prefix (i.e. 'unhappy'). Rozin cites four more such habits. Here's one more: when stating pairs of good and bad words together, it's nearly always the convention to mention the positive word first: as in 'good and bad' and 'happy and sad' rather than the other way around.