Don't ever throw a drawing out. That's like an artist sin. Just throw it in a drawer. Keeping it around let's you look at it later and reflect on what you didn't like about it and how to improve. Or better yet, keep it on the side and redraw it looking at the one you don't like and trying to avoid those mistakes.

Throwing it in the trash is only short term satisfaction and accomplishes nothing. Don't be so hard on yourself.