I've been trying to get into the "writing every day even if it's not good habit". That how you actually improve your writing. It's like riding a bike, you'll never be able to do it if you give up every time you fall.
I write in my "journal" at least once a month. It helps me keep track of life events and how I'm changing as a person. I can already tell that my writing style is developing by looking through some of my older posts.
Related discussion on journals here: http://hubski.com/pub?id=96025
Oh god I know this feeling all too well. Working on short stories to submit to magazines really makes you wonder if you're just being ignored or if you're writing is actually not that good. I still love to write though, even if my stories are sub-par.
That's pretty much how I feel. It's the internal feeling that matters most. Technique can always be improved, but obtaining the drive to keep doing what you enjoy is what really matters. I'm currently having that battle with learning how to program/computer science in general as we speak, haha.