Question

Why is it one thing learning something... but another using it there and then in a game?

Hmm, I guess because sometimes good moves look bad, and bad moves look good!

So maybe we don't trust that the good move works, or when we try to play what looks good sometimes it turns out bad because of some minor detail.

There's also the difference between recognition (recognizing something once you see it) and recall (remembering it with nothing to prompt you). When studying, you might see an idea and after seeing it tell yourself it was obvious... but during a game there's no one to suggest moves for you like this.

I used the stonewell attack against a weaker player and it work.. why do certain things work sometimes and other times it doesn't work?

When you learn something first, it comes to you by intuition and to see or feel that the pattern is there.  But you have to calculate your idea to see if it works too!  As ch said "sometimes good moves look bad, and bad moves look good"  You need to calculate to verify.  When you miscalculate it, you might have the idea but it is wrong due to something you overlooked.

Also you have to actively look for th pattern when you play it in your game, rather then passively learning it.

http://www.dwheeler.com/chess-openings/

Are these good?