If you're reading this, there's a good chance that you question your own judgment regularly.
Doubt is a normal human emotion that tells us much about the world.
When we question our opinions, it's usually in the service of getting better. But sometimes we second-guess ourselves because maybe it's easier to just give up or seek excuses.
But what can you do about it? Perhaps the answer is simply to be curious about your uncertainty. Become aware that you're the cause of this lack of certainty and that you can fix it.
Do you not fully understand the project? Is it a technology you're unfamiliar with? A person you haven't grown to trust yet?
Find that source and resolve it. Become certain, and perhaps you'll learn to second guess yourself less.
