Fog in the Afternoon

I had my voice lesson on Wednesday and my teacher said something to me that will be very helpful. He asked me if I listened to myself when I practice and I said yes. He replied, "Don't." Don't listen to myself sing- focus on the technique. I have heard this before but it's never really sunk in. I listen for things and try to fix and it causes tension (and ultimately frustration). I think this will be really helpful.