Blitz chess is fun and can be a useful way of practicing one's openings, but it turns out to have had another, far more subtle benefit. Psychologists have accumulated and analyzed data based on loads of speed games, and have apparently discovered that regardless of whether one is a "lark" or an "owl" (i.e. someone who prefers mornings or evenings, respectively) a similar pattern holds: we tend to play more slowly earlier in the day, trying to avoid errors (thus demonstrating a "prevention" focus) while later on the tendency is to play more quickly but less accurately (a "promotion" focus).
Plenty of further questions are possible. If one compares the games of players who only play in the morning and compares that product to those who only play at night, will there be differences? Or let's say I play 10 blitz games in the morning, and then 10 at night. Will I play more slowly and perfectionistically in my 10th morning game than in my first night game? Also, which way does the causal arrow go. Do we just play faster (and thereby get slightly more error-prone), or does our attitude change, resulting in faster play? Still another question: is it our specifically "chess willpower" that is affected, or will any depletion in our willpower make us more promotion-focused?
Regardless of the answers to the further questions, it is still potentially useful to be aware that we - and our opponents - are likelier to be a bit "freer" in night games than morning ones.