To stand a chance against more experiences and stronger computer and
human opponents, take a defensive role, especially with computers. 
Hold guard (G) and let them unleash their string of attacks, keeping
in mind to watch them so you can change position to block both high
and low attacks respectively.  When they are done with their
combo, their character will temporarily stall as they gain their
neutral stance, this is when you drop your guard and open up a can of
your own.