I've talked about the value of momentum, how it allows you to create a positive feedback loop when learning a skill. However, there are times when momentum actually slows you down or interferes with the learning process.
When you tax a muscle beyond its ability, you allow it to grow. When you do it right, this process is so intense that it fills up your entire physical and mental experience. Big results come from this kind of effort.
At the gym, you always see dudes putting a ridiculous amount of weight on the barbells and then lifting and lowering as fast as they can. They are letting momentum do the work for them instead of the muscle. A better approach would be to lift far less weight and go as slowly as possible, feeling every sensation on the way up and the way down. This is much harder, and that's why it will pay off.
My piano teacher, John Swiedler, used to tell me, "You should practice so slowly that a listener will not be able to tell what you're playing." Why is this slow playing so important? Because it prevents you from being able to use momentum. This leads to a deeper understanding of the music you are playing. Students always say, "but it's easier to play it faster." Exactly. If it's easy, you're using momentum. We don't want it to be easy. Bwahahahahaha...
"My brain is full."
There's that Far Side cartoon where a student raises his hand in class and asks to be excused, because "my brain is full." Now, part of the punchline is that he has a smaller head than his classmates, but in reality, this feeling happens to those of us with normal-sized brains all the time. It's that feeling you get after staring at a single math problem, crossword, Sudoku puzzle, or highway map for a quarter of an hour with no apparent breakthrough. Believe it or not, very good things are happening in your brain even though it feels like it's melting.
Where this often comes up in music lessons is switching between chords on the piano. One chord is A, the next chord is D. The pianist has to locate the three notes of the A chord, and then find the three notes of the D chord.
Students always rush through this, and sometimes accidentally get the notes right. They are using momentum. Far more difficult (and far more effective) is to slow down and do the mental heavy lifting that this activity requires.
Find each note separately and deliberately. Think out loud. Take note of which fingering will work best, and be consistent. Resist the temptation to rush yourself. Stay completely calm and in control.
It may take you minutes, not seconds, to find the next chord. Paradoxically, however, it is precisely this slow, painstaking process that will allow you to nimbly hop from chord to chord without conscious thought in the near future.
You lifted ten pounds instead of your usual forty and you were incredibly sore the next day. Two weeks of this regimen, and you see muscle definition you thought you'd have to lift eighty pounds to get.
You see that same crossword puzzle sitting on the kitchen table the next morning. All of a sudden, three previously inaccessible answers pop out at you ("Aha! Magnum, P.I.! Elk! Spartacus!").
You lay your hands on the instrument, and you play a difficult passage with ease and precision on the first try.
An unexpected bonus often comes along after a period of concentrated effort. There is thus another layer of paradox here: Take the slow, frustrating path, and it ends up being the quickest, smoothest one. Deliberately avoid momentum in the short-term, and you'll end up gaining a lot of it in the long-term.