How to deal with self doubt?

Hey I've started to noticed that after I do untimed sections or blind review my accuracy is either 80%-100%. From the analytics its also shown me that I often choose the right answer, than talk myself out of the right answeer and end up choosing the wrong one. It seems like I do this fairly frequently. How do you become sure of yourself because this mental block is keeping me in the 155. I know the answer, but than their comes a question that distorts my understanding of what I. believed the flaw initally was. I struggle w/ the Phenomenon-hypothesis (LR) (which seems to be commmon). Do I just need to keep hammering basic principles, or do more questions so I can learn to recongize the pattern in whats being asked?