When you see a top player go for - and usually make - a big shot, is it mindless swinging or tactical shot-making? Actually, it's both.
There are two times when a top player normally goes for a big shot. First, of course, is against a weak ball. From years of training, they are mindlessly efficient at putting anything weak away - and that's not only high balls, but also balls that don't put any type of pressure on the player - from speed, spin, placement, depth, deception, or even extreme lowness.
But sometimes a top player will also rip a winner off a seemingly difficult ball. Is this a mindless, perhaps brainless lucky shot? Sometimes yes, but other times it's because, despite the seeming difficulty of the shot, the player instinctively reads the ball perfectly and is in perfect position, and so is not only able to make the shot, but knows he can make the shot. Two examples might be an opponent who smashes or loop kills the ball right into the player's middle forehand, allowing a relatively "easy" countersmash or counterloop; or perhaps a low, heavy, deep, and angled push - but the player simply reads it perfectly and is in perfect position for the shot, and instinctively realizes this, and so he takes (and usually makes) the shot. It's as if a lightbulb has gone off in his head telling him to take the shot.
And so these seemingly mindless shots are actually high-percentage tactical shots, but only because of years and years of practice and training. And yet . . . they are also mindless. Why? Because, as with all table tennis shots, it is the trained subconscious that guides these shots. The conscious mind just gets in the way. And so while it might be years of training that allows the player to do these shots, the shots themselves are essentially done mindlessly.
How does this apply to non-top players (or top player wannabes)? You too should be training to make these shots. This doesn't mean you should constantly be looking to rip winners (except off weak balls - though even there it's best to only go at maybe 80% and rely just as much on placement), but that you should jump on balls that, after enough training, you realize you have read and are in position for, and then make strong shots. As you get better, your shots will get stronger and stronger . . . until, one day, you might be that "top player" making those "mindless shots."
I often undergo this "lightbulb going off" in my head that tells me that I've read a ball perfectly and am in perfect position for it (as well as when I get a "weak" ball), and when I do, I take the shot - and it usually hits. You too can develop this "lightbulb" instinct. Alas, for most non-top players who often go for big shots, there is no lightbulb going off, and it is just mindless swinging, with little distinguishing between whether they've really read the ball or are in position for the shot - and so their shots are erratic and low-percentage. How to overcome this? Slow down your attacks except when you really see a weak ball or are certain you've read the ball perfectly and are in position for the shot, and soon distinguishing these type of shots will become subconscious habit - and that lightbulb will start to go off in your head.