Well, I can tell you right now that, if you're serious, you're going to get discouraged and you're going to want to quit a bunch of times. In fact, if you don't feel that way, something is wrong. I hate to say it like that, but it's true. The difficult thing isn't even learning the stuff, it's braving the discouragement. But, just stick with it, you'll get there.
That's pretty cool that you're learning All the Things You Are. Here's something to analyze in the tune: look at the chords in the first four lines. Figure out how the first two lines are related to the second two lines.... how they're similar. Do the same with the melody.
lol. playing dream theater songs on drums. lol, I will learn like half a song, and play it all the way up to there. then Mike does starts going insane, and i am like, fuck. skip to next song. lol. I have so many unfinished songs...