Far too often players don't think tactically, believing the game is too complex for them to play and think at the same time. And it's true that you shouldn't be doing any conscious thinking during a point. But between points a smart player does think tactically. The key is to keep it simple.
"Tactics isn't about finding complex strategies to defeat an opponent. Tactics is about sifting through all the zillions of possible tactics and finding a few simple ones that work, and developing reflexive tactics to cover other situations." (That's the opening of my upcoming book, "Table Tennis Tactics for Thinkers.") What does this mean?
The first part means you don't need to fry your brain working out complex patterns or finding ten ways to beat someone. Find two or three simple ones, and that'll usually suffice. Be flexible in adjusting these tactics if they stop working or trying out new ones, but keep it simple.
The second part means you should develop the habit of thinking tactically, and your subconscious will get the idea. It'll soon become automatic - you'll develop reflexive tactics to cover most situations. If you tactically tell yourself to play certain shots in a certain way to a certain spot against a certain player, it soon becomes automatic both against him and against similar players, and you can focus on just two or three other tactics instead. To any experienced observer, you'll be playing a very smart tactical game, but in reality you're only aware of two or three aspects of it. You should be no more consciously aware of most of your tactical play than you would the angle of your racket when blocking a loop - not aware at all. You just do it.
Most tactics should become second nature, allowing you to focus on just two or three things in any given match. And yet you'll be playing many more tactics without even thinking about it, because they will have become ingrained on your subconscious. You'll be tactically placing your shots side to side and in and out, varying the speed and spin, and doing all the tactics necessary to win - and you'll barely even notice you are doing it. What a smart player you are!