- Does perfect practice make perfect? When you practice something with no mistakes at all, will you then develop perfect skills faster? 
For most aspiring guitar masters, practicing without making mistakes all the time doesn't really seem realistic. If you feel the same way you MUST read on. 
In most sports you cannot practice without making mistakes. You can't slow gravity down so you can hit that ball perfectly every time. 

Take your best shot

You must take your best shot and fail over and over and over again until your brain finally creates the connection between different approaches and a successful result. This takes time because you cannot control the process. 
When ever you hit the ball perfectly you feel fantastic. The brain the ties a connection between what you did and the result. It tries to figure out what made you feel all that pleasure so it can replicate it. 

It's a process of constant trial and error until the most advanced super computer on the face of the earth (Your brain) finally gets it. 
It is very true that in most sports perfect practice is simply impossible. You have to make mistakes in order to learn. 

Guitar practice is different

With guitar practice it is the complete opposite. If you are practicing while making a lot of mistakes - chances are you could at least triple the speed at which you develop by eliminating the mistakes almost completely. And the skills you develop when you're not making mistakes will be perfect. 
Practicing is the process of programming the brain to perform movements that doesn't come natural to it. You install new patterns that you where not born with - and that naturally takes some repeating. 

If you program a computer and every 5th line of code contains an error, then you might succeed in creating a program that does something in the end. But it will be full off flaws and bugs. Chances are it will not be of much use when you're done programming. 

Stop practicing and program your brain instead
The same thing goes for programming the brain. You WILL get good at what you practice. And if you're practicing making mistakes all the time, that's what your brain becomes really good at. 
But how then can you become good at hitting a baseball by making mistakes all the time? Well, swinging the bat is one movement. 

It might require a lot of practicing to get that one movement right - and hitting that baseball might be one of the hardest things in the world to do (A champion still fails to hit the ball more than 50 % of the time) 

Hundreds of little movement versus one

But hitting a baseball is still just one movement, however complex it might be. Playing guitar is hundreds of little movements. And it would not be possible to learn to perform all these little movements if you had to use the method of the baseball. It would take you several lifetimes to achieve even a mediocre skill level. 
If practicing without making mistakes seems almost impossible to you, then you will benefit massively from focusing on not making mistakes. Slow down. Relax. Do it perfectly. 

The most effective path to mastery

This seems counterintuitive but it's the most effective path to mastery. And you will spend your practice time building perfect skills. 
This rabbit whole goes very, very deep. If you're struggling and have been for months or years, this could very well be your straight road to the skill level you want. But you have to fight against the urge to practice fast with mistakes. 
Practice fewer things. Narrow it down to a couple of simple things you want to focus on for the coming month. Then decide to practice them with no mistakes, what ever it takes. Do it for at least 4 weeks. 

Then judge by the results you get.