Why "practice, practice" is often terrible advice
"I am sick and tired of being sick and tired."
— Fannie Lou Hamer

I have been on countless forums and subreddits. They all say the same thing.
Someone asks:
How can I get better at X?
What is the secret to being the best at Y?
Top tips on how to master Z?
They always reply: "Practice, practice, and practice some more until you (magically) get it."
On Quora it is particularly common that people ask questions like:
How can I improve my guitar skills?
Can I learn to be a great guitarist by myself?
Why can't I play cleanly on my guitar?
Yet again, the answer people give tends to revolve around "more and more practice".
For someone without experience, yeah, it does sound reasonable. I mean, you do need time to perfect your craft, right?
Well...yes...and no.

When I first started to play guitar, I was around 15. At that time, it meant pretty much the world to me, so I would spend a lot of hours a week practicing, and practicing, and practicing some more. Don't get me wrong, it was tough but it did pay off quite well, since I did get the hang of the instrument reasonably well in just a couple of months.
As a teenager, I would spend my time with practicing the guitar and playing video games, and that was pretty much it. Of course, it was great back then, since school was not much of a hassle.
But...it did not last. Sooner, rather than later, the excitement of seeing rapid growth in skill starts to fade. This is natural for every activity you can possibly do. This is sometimes referred to as reaching a plateau, which means you reached a level of skill that does not improve any longer (or at least seems that way). I'm pretty sure you've reached plateaus in many activities in your life too.
I believe the most popular plateau comes in the fitness industry. Who doesn't want to get the elusive six-pack abs? Most people do not get it despite working out on a regular basis, so why does this happen?
Do you know what most people do when they get to a fitness plateau, that is, they suddenly don't seem to get any leaner? Well, they start thinking things like:
"If I only put in more effort, I'll make it."
"There has to be something I'm doing wrong."
In some extreme cases, they might feel:
"This doesn't work. It's all a scam!"
And then they'll quit whatever it is that they wanted to achieve, only to then feel guilty about others making it and they not.
The six-pack abs will continue to be in a tiny part of their memory, forever to be reminded about.
What happens when we start seeing that despite the time and effort we are puttin in, we are not seeing the results we expect? Of course, we start to question ourselves, which usually leads to second thoughts.
It was Albert Einstein who (supposedly) once said:

"The definition of insanity is doing the same things over and over again and expect different results."
It doesn't matter who said that. What matters is that it does teach us something invaluable. If you feel like you are not gettig the results you want, you will have to change something in your approach, unlike what most will think that they have to do even more of the same until they finally make it.
So, dear friend, what does this mean?
It means, at least, the following:
You will reach plateaus.
Expect them.
Be prepared.
Don't be afraid to try new things.
What you need to know, at all times, is that you need to acknowledge that reaching a point where you feel you cannot go past it, does not mean there is anything wrong with what you are doing.
Persistency and effort alone can only get you so far, and you will have to change your angle and strategy at some point.
Remember that: no pain, no gain, but enough pain is enough gain.
Nobody ever got to be a great cook by cooking one single dish, right?
Why would it be different with you?
Play smart.