Why it's important to not have any bias?

 EURUSD M15

 EURUSD H1 (Friday early morning GMT)

 USD index - rising wedge (usually strong move can be expected)

EUR index - after breakout, it even came back to the apex.

Why you should take the trade on Thursday around 6pm GMT?
Just analize those 4 screenshots above.
I admit, I didn't take it. The reason I missed it was my strong bias to be short EURUSD below 1.2440.
Seeing all this, plus watching break below 1.2440 not very convincing - I should know better.
BTW I'm not showing it trying to be a smart ass after the fact.
All I want is to bring to my, and your attention how psychology + having bias can make you miss a very nice trade. And I'm not saying that next time it's gonna be the same. I'm saying that it was worth to take that trade and next one like that, because the risk was small... TRUST THE CHART, IGNORE THE STORY...