So what does it take to win a game? Any game? What does it take to gain the maximum amount of odds in your favor? Exactly that! Getting the maximum amount of odds in your favor! Confused? Let me explain.
So back when I watched Naruto I saw this scene of Kakashi trying to fight some villain (sadly I cannot recall the scene, maybe someday..). Anyway Kakashi, the analytical ninja, put his analytical mind to work and noticed that his opponent did not make a single wasted move. All of the moves his opponent made in combat were with purpose, and always on point. Kakashi had to dodge the moves to not get hit, putting him on the defense.
Now the same holds true in cardgames. When you make mistakes, they will end up mattering, no matter how small. Now this does not mean that you have to stop making mistakes, because that is impossible. But it does mean that you need to intend on not making any mistakes. You need to play every turn with the intention of making the best possible play (in your opinion). This powerful focus will also allow you to improve a lot faster than quickly playing and ending your turn, not giving much thought to the endless amounts of plays available each turn.
So next time you are in a duel and you start your first turn, take your time to analyze each play available to you and pick the one you think is best. Do this every turn and you will quickly see your skills elevate!