i realised this too, as i only learnt bits of songs and very few full songs... but then i looked at my technique and its solid (thanks to my classical guitar lessons when i was little).
So the only thing ive changed since then is to learn the whole song and if i find a bit i cant do i skip it and go back to it slowing it down then with a metronome speeding it up till i can play it faster than im supposed to, this way i dont get annoyed with my self that i cant do it and end up learning more songs.
So i completly recommend people using metronomes its 1 of the most handy things ive got and if u slow parts u cant do right down and then slowly build it up to the right speed (or even faster like i do cuz then u know u can play it properly) ure speed and accuracy will get better and u dont get stressed out so much... I also use it to learn scales and things so i can improv' solos and things and then i know what notes i can play and what 1s sound good.
Using the metronome with Rusty Cooleys Legato workout is a god send, rediculous streaches that u are rarly going to use but all builds to gether to increase speed.
Oh and another thing ive stopped doing is cracking my knuckles feels good but then they stiffen up again and makes playing faster harder...
just some lil tips...
BigT