I remember those same feelings. It's tough to feel that way, but you feel frustrated because you are interested, and that's the most important thing of all. As long as you remain interested, you'll keep working at it, and eventually you'll be very happy you didn't give up. But don't spend too much time beating yourself up over not being able to write something 'complicated' ... I assure you that one day it'll all 'click,' and your definition of what is complicated will summarily change. And you'll feel like chuck norris.
Makes me mad at myself (for my slow progress) when I come on here and see people asking questions about complex code that I'm not even nearly close to knowing, when I'm only up to the seventh lesson. =/.