When on defense focus on jabbing at your opponent and not lunging. Jabbing is a thought out move to confuse the defense. A quick step to make the offensive player think you’re going one way when you’re actually going another direction.
For example, you’re on defense and you jab to your right to make your opponent to go left, when the whole time you wanted him to go left and you’re still in a solid defensive stance.
If you would have lunged in this scenario to try to steal the ball, and failed, your defensive stance would have been lost and your opponent would leave your jock strap hanging.
The lunge is an attempt to steal the ball, most likely resulting in failure and your opponent going by you to score a bucket. Lunging also causes fouls because you commit your body to a direction without any control over it.
Learn to jab and never to lunge. Staying in front of your defender and forcing a turnover though good defense is more important than risking your defensive position with a lunge.