Learning From Practice Games (and other people's mistakes)

There's only a certain amount of rated (official) games that one can play. Given this fact, it's important to learn from other people's mistakes and to learn from mistakes made in practice (unrated) games. If you only learn from rated games, you are going to lose many rating points before you start gaining them back. Why not learn from practice games with friends or blitz games played online?

Below is a practice game I played with a friend and how just a week later how  I used what was learned to win a game.