I've been drawing for quite a while, but I didn't take it seriously. So, I usually just throw away many of my sketching.
You're maybe wondering the x's at the bottom of the first image. Can't help it. I got a degree in electronic engineering and discovering pattern is essential in mathematics.
The one done in sketchbook is, well, just for playing around.
The photos are all from 4chan. Don't know if that's important.
I have to ask though, is it really essential to keep your sketches?
And I wonder if it's okay to use A4 printer papers instead of 'real sketchbook'. I admit the real one feels much better but I can get A4 papers for free from my lab, hence, save money.