When you hire a professional, what you’re hiring for is thoroughness. When I look back at jobs I’ve done in the past, mainly translation jobs, I can see areas where these days I would be much more thorough.
This insight only comes with experience, and we can’t change what we did in the past so shouldn’t worry about it. However, when you’re hiring a professional, you’re hiring someone with the experience to know when and where to be thorough. Then it’s a matter of trust in that person to deliver on that thoroughness.
To be thorough takes generosity of time and effort, and that’s why some things take more time and more money to do. If you want to become a professional, be thorough in all that you do.