Meditation

Focus is something that's essential to good guitar practice and playing. By focusing, one can increase the value of any time spent on the instrument, meaning that if you focus, you won't have to practise as much to obtain the same results, this is why some people can do in 4 years what some could never come close to in 30 years.
To be able to practise guitar properly and not be distracted by the thoughts bouncing around your head, you must clear your mind, the way to do this is through meditation.
Meditation is a skill that can be practised on its own but can also be practised with the guitar. The way to do this is to sit down with your guitar and have your fingers do something that doesn't require a lot of thought, like forming a chord or performing a stretch, then meditate.
There are many resources online teaching how to meditate but the number 1 thing I've noticed about meditation is that it's not something you DO, but it's a bunch of things you DON'T do. So when you practice, forget about:

- How good you think you are

- Whether what you're doing is difficult or not

- Whether you should already be able to do this or not

- Everything

This sort of goes hand in hand with the idea of convincing yourself that what you're doing is easy, professed by many great players, except we're taking it a step further and just forgetting about what's easy and what's hard in the first place. Telling yourself something is easy is also telling yourself something else is hard, just forget the whole notion of difficulty.
Also a useful thing to remember is that if you start to think that it's boring, you're not doing it right.