Your mind has 70,000 thoughts a day. Clearly, some of those 70,000 thoughts are going to be shallow, irrational, inaccurate, or just plain dumb. And yet we never generalize from those few dumb or irrational thoughts and leap to the assumption that we are dumb or irrational, right?
Therefore, don't do the same with your writing. Don't generalize from the last dumb thing you've written and conclude that you're dumb too. You're not. The two things have nothing to do with each other.
If there's one fundamental message I have for you here at QWT, it's this: you are not your writing. Don't identify with it, or get caught up in the idea that it's a reflection of your intelligence or your value.