[3dFlatLander]

I know exactly what you mean, and I'm only beginning to overcome my 'bad design sense'. Since I started coding before designing, I've found it helpful to draw parallels between the two. Like studying good code helps improve your own programming skills, finding and examining what makes a design 'good' is extremely helpful. I've got a huge folder of code I use over and over again, improving it as time goes on. Likewise, I've started to keep a folder of design components -- layout ideas, button designs, gradients, as well as links to the previously mentioned 'good designs'.

Edit: This sounds like common sense now that I read it over again. Sorry if it's not helpful.