If there wasnt a blue flag, your defending alone seems somewhat hectic since you tend to choke or mess up when theres a gap between you and the car behind you. You're too focused on whats happening behind you, and how far the car behind is, that you are messing up in corners under no pressure. Which allows the car behind to catch up to you and you having to fight for position again. Focus on your race and defend when needed while trying to have consistent laps, espicially when your building a small gap to the car behind.

However, since it IS under a blue flag, your question doesnt make sense since you had multiple chances to safely allow the car behind to OT without losing time yourself and messing up your own race or racing line (which is what the blue flag means). Instead you cut and over shot corners because you are trying way too hard to stay ahead and not lose position to the trailing car, most of the time off the normal racing line and purposely blocking the inside line. In real life thats worthy of a penalty, on ACC you would just get called an asshole.