Its okay to listen to that inner voice so long as its telling you positive stuff. Your mind doesn't hear "Don't ....." so for example, if I tell you "Don't think of a blue tree" What do you think of!!!?? thats right you thought of A BLUE TREE - but I told you NOT to!!! Get it? So if your inner chatter is saying "Don't fail" or "Don't do it wrong!" what is is actually hearing ??? Fail!! Do it wrong!!! You can't NOT think of something you have brought to your mind.. so always think positively..... "Lets go and get this test done!" "Lets go in there and ace it!" much better than thinking negatively eh?
When you're really struggling and it feels like a million voices are screaming at you "you CAN'T!" quieten them and listen to the one tiny voice that believes in you and whispering "You CAN!"