If you’re not falling over and stumbling from time to time it means you’re just coasting.
It’s when you push yourself, go outside your comfort zone or try something new that you make mistakes and stumble. That’s no bad thing. It’s part of the learning process, and the very fact you’re making mistakes is a sign of progress and a sign that you’re pushing the limits of your capabilities. It is at this stage that you grow.
So next time you struggle with something in your PhD or you find a new part of the PhD journey hard, remind yourself that you wouldn’t have made any mistakes at all if you were just coasting through. Instead, you’re pushing yourself and you’re growing as a result. Your mistakes are testament to that. Embrace them.