Confirmation is an insidious little malady that afflicts everyone at some stage. Our natural desire as members of a herd is to find people who agree with our point of view. In trading this takes the extreme form of overweighting opinions that match ours and underweighting those that disagree with us.
The natural tendency when holding a position that is going against you is to seek some form of assurance or confirmation that your original decision was correct and therefore needs no alteration or action. So in many ways this bias is merely a means of ignoring the reality of a situation by seeking comfort in the opinion of others.
The solution is at once simple and very hard. Use your own judgement – if it has gone wrong then it has gone wrong.