>If you mess up, redo the part you messed up correctly 5 times in a row.

I think it may be important to note _when_ to redo this. I started off this way, but after working with a guitar teacher (a Berklee graduate), he recommended that I continue on with the song and return to the problematic parts afterwards. If you constantly stop at the problematic parts to replay them and get it right, you'll have no idea what other parts you'll have trouble with further into the song until much later. In addition to that, being able to move on and continue playing the song after making a mistake is an important skill itself. If you build that skill, it's usually only other musicians that will notice -- a regular audience won't.

What's your take on it?

As somebody who started teaching himself guitar as a teenager, put it down for 10+ years and started back up, this resonates.

Everything takes twice as long to learn because I first have to unlearn the old habits.

Yes. Put another way: Slow is smooth. Smooth is fast.

And as my music professor once said: "If you sound good while practicing, then you're not practicing."

Time is the largest factor though. Some ways are better than others but there is no substitiute for time.

why am I posting here instead of practicing?

Practice make permanent.