I've been drawing for many years and keeping sketchbooks has always been a difficult part of that process, the history of my work is on envelopes, in math books and lose paper all over my room. Somewhere along the way I got into the idea, that sketchbooks have to be perfect, however that's not the purpose of a sketchbook. They are a big part of the learning experience, something to pick up and take notes in, to be messy, a place to think freely. There are no wrong answers. I used to tear pages out and gave up on sketchbooks altogether when the first few pages did not go well.
I still find it daunting to begin one. But have seen so much progress from overcoming this mental barrier, I really recommend you to start a sketchbook and use it as much as possible. You learn so much and have a great record of how far you've come, when you need that little boost in times of doubt.
So I thought I'd share some work from my 2016 sketchbook, I selected some of my favorites, but if you want to see the whole book with messy awful doodles and terrible commentary then feel free to check out this video: 
Thank you for reading and watching. As always feel free to ask questions and let me know if you have any requests, I will try to get back to you as soon as possible :)
Have a great day!