Throughout my life of a mere 31 years I have had to learn in 2 main ways. Taught-by-other(s) and taught-by-self. I've studied computer programming at college.. and before and after that I self-taught myself. I've studied at university but only by correspondence.. so in that sense I was really self-teaching myself with a structure set out by others. Same with guitar.. same with a lot of things.

When you are self-teaching, even with a structure set by others, it is really a matter of pushing yourself outside of your comfort zone and that is when you really start to learn. Playing the same old stuff again and again, even if you are trying to find new ways to play it, is still inside your comfort zone and while you will learn a great deal over a length of time, pushing yourself outside of the comfort zone will get your learning so much faster.

Ever tried slide-guitar? Why not? It can be used it just about any type of music.. may be not in its traditional sense but if you are holding a solid object against the strings and sliding it back and forth to get microtones, then you are playing slide guitar. You will never know unless you try it and get out of your comfort zone.