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
At the start of each match, you should have a game-plan as to how you want to perform.  Knowing yourself, you probably know which 5-6 serves best setup your game, which strengths that you want to use, and which patterns that you commonly play.  If you begin losing the match, then you need to tweak your first plan.  Instead of merely serving the same serves, consider changing them slightly in spin, speed, depth, and placement.  Instead of looping your normal way, consider adding more variations.  Instead of blocking how you normally block, push yourself to do something different.  Making those adjustments during the match is necessary to change the momentum during a match.
 
 
Plan B Changes
As the same match progresses, you realize that making minor adjustments to plan A really isn’t working.  So, you decide to go to plan B.  Plan B is a totally different game.  Instead of playing your normal game, you completely adjust your style to hit on your opponent’s weak point.  Let me illustrate:  let’s suppose that you are a looper who typically serves all short backspin serves and loops slow spinny consistent loops.  You are playing against a blocker, who doesn’t loop well, but can beat you with his quick blocks.  Changing to plan B might be to serve long, push long, and allow the blocker to loop first.  Once he has looped first you counterloop for a winner.  Although this isn’t you main style, you give it a try because you are down 2-0 in games and losing 5-1 in the 3rd.
 
Generally, adjusting and re-adjusting your plan A game is the safest tactic because it allows you to stay within your comfort zone while giving your opponent good variation.  However, there are times when play A isn’t working.  Consider practicing your plan B or even plan C game at the club from time to time.  You never know when it will be necessary.