When to test and why?

Tracy
Alright ladies. I have seen SOOO many of you posting your pregnancy tests questioning if it is a BFP or line eyes. What is the reasoning for testing so early? I have always told myself I was not allowed to test until AF was at least 3 days late, but this month that date is Christmas. And after a recent MC I am a little emotional and I really don't want a BFN on Christmas Day.