The above should be on a banner at every playing hall in the world. Players almost always try to drill at speeds or with power they can't control, thinking that by drilling that way, they'll learn to play at that pace. Superficially, it makes sense. But in reality, trying to play at a pace you can't control leads to sloppy, rushed technique, and poor balance, and so you are just reinforcing bad habits.
Instead, drill at a pace that you can control, both with consistency and where you can keep the ball roughly where you are aiming, while staying balanced throughout. Focus on developing good technique, which is the difficult part to master. By going at a slower pace, you can reinforce and perfect that good technique until you can practically do it in your sleep, which should be your focus. Because if you develop good technique, you will be able to play with speed and power - see the title of this article.
What you can and should do, when you are practicing at a pace you can control with at least decent technique and balance, is occasionally smash or rip a loop, just to test the shot. You'll find that with good technique, this is easy, as long as it isn't forced, i.e. you don't try to rush it when you are not ready for the shot. You can also work on playing at a faster pace in multiball or on a robot, where every ball comes out the same, and so you can increase your speed and power and still have control and consistency.
Where did I learn this lesson? It comes from many decades of coaching experience, but it originally came from a specific incident back in my first year of play. At some big tournament I saw U.S. Men #1 Danny Seemiller (soon to be 5-time U.S. Men's Singles Champion) warming up by doing simple side-to-side forehand footwork at a nice, consistent pace with his practice partner and brother, Ricky Seemiller. I remember thinking to myself, "I can do that faster than he's doing it, and he's the best in the country?"
Then I practiced it with someone, and of course I did do it faster than Danny - except I would hit maybe three raggedly rushed shots and miss, my shots were spraying all over the table to my partner's chagrin, and we couldn't have a good rally. Then I slowed down to a pace about the same as Danny and Ricky were doing, and suddenly I was consistent - everything came together, and my shots were fluid and consistent. I was hitting like Danny Seemiller!
From there on I always did footwork and other drills only at a pace I could do consistently and comfortably, with good technique. This doesn't mean you don't push yourself, it means you push yourself at a pace you can do consistently.