Hello there, It is a good therapist that will think about how you could have done things better or differently.
It is called "reflective practice" ,and quite a normal thought process which helps you to work out alternative ways of doing things. Better, quicker, more accurately, best use of time, neat work etc,etc.
I noticed your eyebrow blister post and replied to that, I think you are going through a shakey patch that's making you lack confidence and think you are not any good at your job.
You are only 3 years into your career ,please don't be so hard on yourself. Your attitude to wanting to perfect all you do is exacty how it should be! This will not be the only time you feel like this. I have been self employed for over 25 years, and get situations that I feel like I am losing my work quality. I am not .
All the best thoughts to you
RosieR