Clavicles show in the center but get covered up really quickly by the pectoral and the rest of the arm when in that position.
Do you keep your pinky wrapped in, pointing towards your thumb as you hold your pencil? Try pushing all your fingers out before you hold your pencil, like the OK sign, and then put pencil to paper. There's a lot of other recommendations out there about holding the instrument vertically and some other stuff too which alleviate this problem.
Like ash+bones said, don't worry about spending too much time on something when you first get into it. The speed gains when you get familiar with something are so massive it's pointless to try and comprehend what it'll be like then. There was one drawing where I tried to draw five heads and it took me the better part of 10 hours just to set it up; I can now do that amount of work in a little over 10 minutes. It's automagical.
This is good. It'll be useful any time you want to get a feel for something the whole way around. Note that the reverse of any given position will always have exactly the same contour.
Sketchbooks are a record of our art, it's only natural that there's also some extra notes that come along with them.
I'm not a fan of "getting out of your comfort zone" though.
The concept itself is not incorrect, but it's said too often and often told to people who don't need to hear it, because they naturally explore at a lower rate, and when they hear "get out of your comfort zone" they do things too wild, then overcompensate the other way and only stay in their comfort zone. I'm one of those people in this case, and in a lot of cases I'm also one of them. I think gestures for beginners are a big meme, for example, if you haven't a clue about anatomy or how to somewhat-accurately place multiple forms in perspective. Doesn't stop people from telling beginners to start with gestures. Even though grandmaster animator Vilppu said, in one of his New Masters Academy videos, that gesture only builds upon perspective and anatomy, and if you don't know either, you should go work on them first.
I'm the same as you in that I basically never do personal pieces, because I think it's largely pointless in the scope of all the other things I could be doing to get good. It seems a lot of people love drawing/painting and get better as they make a lot of big pieces, which is great for them, but when I do them I just feel like crap and don't want to do it anymore. What used to happen was I believed that I had to do big pieces in order to draw (because otherwise I'm a "doodler"), which only made me not draw much at all until I was "inspired". Recently I decided to go entirely the other way and trust what I actually felt, which was that drawing personal pieces is pointless if I don't want to do them, screw what anyone else says. So I don't anymore, until I seem to have run out of things I think are major problems, at which point I do a big piece, and so far, every time I've done it, I've ended up with a lot more major problems to solve, which I'm perfectly happy to drill construction or perspective or anatomy or whatever on.
Maybe I have no knowledge about color theory, only a trivial understanding of rendering, and can't do gesture or bargue or whatever, but I'm putting in the hours, and I'm improving at what I'm working on, I'm doing more work and getting better at a rate I've never had when just following other people's words. Comparing myself to myself, I've never been better. It's not actually true that I "could have been spending time on color theory" for example, because I don't think color is more important than what I'm working on. If I was forced to do color first, I'd basically just not do it.
At least in my opinion, doing things is more important than checking off boxes on other people's lists of what I'm supposed to be doing.
sorry for the blog - tl;dr just make sure to check with yourself every once in a while to make sure it's what you want.
[Yukio] Mishima had been asked, “What is the passion that drives you?”
He replied, “Being brought up during the war and being told at the age of 20 that everything until then had been a mistake — that’s all.”[Sketchbook][Imgur][FB]