First of all, how it makes you feel. And then also logic. Very few people will give you constructive criticism, because very few people care for your wellbeing enough to spend time and energy at it. It's usually parents, very close and trusted friends, etc. Most often I can identify how the person giving the criticism would benefit from my doing/being as they say and I dismiss the comment as their personal interest.
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So-called white lies are like fake jewelry. Adorn yourself with them if you must, but expect to look cheap to a connoisseur.