Gratitude is the only acceptable way to acknowledge someone's kind remarks. Sincere thankfulness won't give off the appearance of pride or vanity. Instead, it shows you acknowledge a person's recognition and appreciation.
Deflecting a compliment is not modest or unpretentious; it's actually a bit rude. After all, someone has taken the time to not only notice you and your efforts, but has gone a step further and actually acknowledged it.
It can feel unsafe and vulnerable to receive compliments and take them to heart. If we quickly return the energy, we can stay in our comfort zone and we obstruct the intimate and heart-opening growth before us.