Yep, that's so me as well. It's a good and bad thing. You'll never stop improving but on the other hand, you can have depressing periods when you think you're no good at all (I guess that's why they say artists are moody lol). That's why it's good to have people who like what you do. Of course, you can't only rely on praises (or you wouldn't improve), but they're sweet to hear. And... well, sometimes, there is a work of yours that you're still proud of.
Basically feel like this with everything I do. Though it's a good thing. It pushes me to always try harder and be better at what I do, whatever it is. For example, I've been doing some profile drawings on post-its, I started during my finals session to relieve stress in between tests, and it turned out like crap at first but I kept going since I wanted the crap to look all right. (Yessss, even if it's on a stinking post-it, it's not the media which makes the artist but what the artist does with the media to make art.) I will never feel completely satisfied with my creations since I'm always growing and my style keeps on changing with what ever new thing I try. There is never an end to learning and exploring. I like your little strip since it's so true to what I feel