In part 3 of the interview with Tia-Clair Toomey, she discusses her best and worst personality traits. She reveals her competitive nature as her best trait, which fuels her drive to excel in CrossFit. She also opens up about her worst trait, stating that she can be overly stubborn and set in her ways at times. Tia acknowledges the need to work on this aspect and embrace more flexibility and adaptability in her life. Overall, she remains focused on self-improvement and growth.