Plan A vs Plan B
 
If you are winning a match, then typically you will keep your tactics while making minor adjustments in your shot selection and giving some variations in your shots.  If you are losing a match, then typically you will need to make more changes.  If the match continues as it started, you will lose.  So, you will need to decide to push yourself to make the necessary changes.
 
What kind of changes need to be made?
 
Plan A Changes