For example, I was taught in college that one ought to figure out a program
completely on paper before even going near a computer. I found that I did
not program this way. I found that I liked to program sitting in front of a
computer, not a piece of paper. Worse still, instead of patiently writing
out a complete program and assuring myself it was correct, I tended to just
spew out code that was hopelessly broken, and gradually beat it into shape.
Debugging, I was taught, was a kind of final pass where you caught typos and
oversights. The way I worked, it seemed like programming consisted of
debugging.

For a long time I felt bad about this, just as I once felt bad that I didn't
hold my pencil the way they taught me to in elementary school. If I had only
looked over at the other makers, the painters or the architects, I would
have realized that there was a name for what I was doing: sketching. As far
as I can tell, the way they taught me to program in college was all wrong.
You should figure out programs as you're writing them, just as writers and
painters and architects do.

Paul Graham
"Hackers and Painters" - http://www.paulgraham.com/hp.html