NiftI'm a new member but have played GT3 off and on for a year and GT4 for a few weeks now.
As others mentioned, you have to put it down for a while. It happens. For example, in GT3, there was an exam where you had to go through these turns that kept getting smaller and smaller. I must have tried for a week to complete that thing. The longer I stayed with it, the more frustrated I got.
One evening before I went out, I turned it on while waiting for some people to pick me up. Jumped over to the test and hit it the first try. I didn't even sit down to do it.
I don't worry about golds or anything. If they happen they happen.
I did something similar with Test 15 on iB. Couldn't get round the course without losing the back end and spinning out. In the end I decided to leave it a week and come back to it. I passed it first time (although not gold) - in the end I decided that you can actually try TOO hard and this causes you to make mistakes.