Practice makes perfect?
It's an old adage - "Practice makes perfect" - and the general concept is true, the more you do something the better you get at it. There is however a fundamental flaw with this sentiment. What if you are practising the wrong thing?
I believe that it is during a guitarists' practice that he/she truly learns to play the instrument. Any guitar teacher can show you a few chords and scales, but unless you put the work in yourself you are not going to progress. Another stumbling block for many students is practising the wrong thing. If you learn a new chord but spend all week practising it with one of your fingers in the wrong place, you will get really good at playing the chord wrongly. This is where you must make sure you understand what your guitar teacher is showing you. Always ask questions if you don't understand fully - that is what your teacher is there for!