Truth may be that sometimes the duel is lost in failing to drive few corners effectively. Defending depends hugely on the position of the track. I think the main defensive weapon is the knowledge about track and car. It's stupid to take any other line than the "best" racing line in some places, but for some curves (quite many actually) ad hoc lines usually work pretty well.
I love making the car as wide as possible without jerky sharp line changes. The defensive line starts from a turn and is pretty much choosed before that or in it. I'm quite static and erratic
when defending my position, and sometimes that's just enough. Most of the times my strategy envolves counter striking. It's always easier to put pressure on the racer in front, so I usually "force" the compatitor to make foolish passing attempts or I just let them by and begin to pressurise.
Contacts are no-no. Intentional contacts are disapproved and accidents/mishaps are embarassing.
Defending position for several laps is quite an adrenaline rush, but constantly fighting for position through several position changes is
the rush.